A mark was eight ounces of gold or silver. Therefore 100 marks of silver would be equivalent to $4,000 at 21st Century prices, and 100 marks of gold, $400,000.
Depending on the period and place minted, there were anywhere from 48 (Visigoths, 6th Century) to 125 (Castile, 14th Century) gold maravedi to the mark. In the Cid's time, the value was around 57 to the mark. There were ten dinero to a maravedi.
But he answered, Far be it from me that I should take from your Monastery what the good men before me have given to it! Take ye back the crown, and take also ten marks of silver, and make with the money a good cross, to remain with you for ever.
He must have six hundred marks.
Well then, said Martin Antolinez, ye see that the night is advancing; the Cid is in haste, give us the marks.
And they made answer, Martin Antolinez has covenanted with us, that we shall give you six hundred marks upon these chests, and keep them a fun year, swearing not to open them till that time be expired, else shall we be perjured.
Take the chests, said Martin Antolinez; I will go with you, and bring back the marks, for my Cid must move before cock-crow.
And when they had placed the chests in safety, they spread a carpet in the middle of the hall, and laid a sheet upon it, and they threw down upon it three hundred marks of silver.
And the Jews said to each other, Let us give him a good gift for this which he has done; and they said to him, We will give you enough for hose and for a rich doublet and a good cloak; you shall have thirty marks.
Don Martin thanked them and took the marks, and bidding them both farewell, he departed right joyfully.
When Martin Antolinez came into the Cid's tent he said unto him, I have sped well, Campeador! you have gained six hundred marks, and I thirty.
And the Cid told him all that had befallen him, and how he was a banished man; and he gave him fifty marks for himself, and a hundred for Dona Ximena and her children.
And the Cid divided the spoil among the knights and foot-soldiers, to each his due portion; to every horseman a hundred marks of silver, and half as much to the foot-soldiers: and because he could find none to whom to sell his fifth, he spake to the Moors of Castrejon, and sent to those of Fita and Guadalajara, telling them that they might come safely to purchase the spoil, and the prisoners also whom he had taken, both men prisoners and women, for he would have none with him.
And they came, and valued the spoil and the prisoners, and gave for them three thousand marks of silver, which they paid within three days: they bought also much of the spoil which had been divided, making great gain, so that all who were in my Cid's company were full rich.
And salute for me the Abbot Don Sancho, and give him fifty marks of silver; and the rest of the money, whatever shall be left, give to my wife, and bid them all pray for me.
And in this time King Fariz got well of his wound, and my Cid sent to him and to the Moors, saying, that if they would give him three thousand marks of silver, he would leave Alcocer and go elsewhere.
And King Fariz and the Moors of Techa, and of Teruel, and of Calatayud, were right glad of this, and the covenant was put in writing, and they sent him the three thousand marks.
Thus was Count Ramon Berenguer made prisoner, and my Cid won from him that day the good sword Colada, which was worth more than a thousand marks of silver.
And in one of these skirmishes, a rich Moor was taken who was Alcayde of Acala, which is near Torralva, and they gave him grievous torments till he ransomed himself for ten thousand marks of silver; and moreover he gave the houses which he had in Valencia, which were called the houses of Anaya, to be theirs if peradventure the town should be yielded up.
Every foot soldier shared a hundred marks of silver that day.
Moreover he bade them take a thousand marks of silver to the Monastery of St. Pedro de Cardena, and give them to the Abbot, and thirty marks of gold for his wife and daughters, that they might prepare themselves and come in honourable guise.
And he ordered three hundred marks of gold to be given them, and three hundred marks of silver, to redeem the chests full of sand which he had pledged in Burgos to the Jews; and he bade them ask Rachel and Vidas to forgive him the deceit of the sand, for he had done it because of his great need: and he said, You, Martin Antolinez, were aiding and abetting herein, but praised be the name of the Lord for ever, he hath let me quit myself truly; tell them that they shall have more profit than they asked.
And he ordered three hundred marks of gold to be given them, and three hundred marks of silver, to redeem the chests full of sand which he had pledged in Burgos to the Jews; and he bade them ask Rachel and Vidas to forgive him the deceit of the sand, for he had done it because of his great need: and he said, You, Martin Antolinez, were aiding and abetting herein, but praised be the name of the Lord for ever, he hath let me quit myself truly; tell them that they shall have more profit than they asked.
When they reached Burgos they sent for Rachel and for Vidas, and demanded from them the chests, and paid unto them the three hundred marks of gold and the three hundred of silver as the Cid had commanded, and they besought them to forgive the Cid the deceit of the chests, for it was done because of his great necessity.
And he gave the Abbot the thousand marks of silver which the Cid had sent for the Monastery, with which to discharge all the debt that Dona Ximena and his daughters had contracted.
Wife Dona Ximena, said he, these damsels who have served you so well, I will give in marriage to these my vassals, and to every one of them two hundred marks of silver, that it may be known in Castille what they have got by their services.
The Infantes I put into your hands; they will go with you, and I shall return from hence, and I order that three hundred marks of silver be given to them for their marriage, and they and your daughters will all be your children.
My Cid Ruydiez the Campeador returned from the slaughter; the hood of his mail was thrown back, and the coif upon his head bore the marks of it.
Great joy was made in Valencia for this victory, and great was the joy of the Infantes of Carrion; five thousand marks came to them for their portion of the spoil.
And the Cid gave unto his sons-in-law great store of cloth of gold, and of serge, and of wool, and a hundred horses bridled and saddled, and a hundred mules with all their trappings, and ten cups of gold, and a hundred vessels of silver, and six hundred marks of silver in dishes and trenchers and other things.
I gave them, when they took my daughters from Valencia, horses and mules, and cups and vessels of fine gold, and much wrought silver, and many noble garments, and other gifts, three thousand marks of silver in all, thinking that I gave it to my daughters whom I loved.
Then made they their account with the King, and it was found that what they had expended for his service was two hundred marks of silver, and the King said that he would repay this, so that there remained for them two thousand and eight hundred to pay.
Who can tell how nobly the Cid distributed his treasure before he departed? And he forgave the King the two hundred marks which should have been paid on account of the Infantes.
And he laid before them great store of gold and of money, which came in leathern bags, each having its lock; and of wrought silver in dishes and trenchers and basons, and pots for preparing food; all these of fine silver and full cunningly wrought, the weight whereof was ten thousand marks.
Then he brought out five cups of gold, in each of which were ten marks of gold, with many precious stones set therein, and three silver barrels, which were full of pearls and of precious stones.
And to the other knights who had not served him so long, to some a thousand marks of silver, to others two, and some there were to whom he bequeathed three, according who they were.