The Bechora: How much was it worth?

We recently learned about the birthright that Esav sold to Yaakov for a bowl of lentil soup. I saw an article about relative values of things based on desire.

The beginning of the article spoke about how the bechora MUST be worth more than a bowl of soup! It then went on to tell a story about a man that needed money to pay for his daughters wedding. His rebbe told him to take the first business opportunity he found. He was in an inn and a rich man decided to make fun of him, so he offered to sell the poor man his Olam Habah for one ruble. The poor man accepted, thinking of what his rebbe had said. The rich man went back home and told his wife what had happened and she freaked out and sent him to buy it back. The poor man initially refused until the rich man offered him the exact amount of money he needed to pay for his daughter's wedding.

The article concludes with an interesting thought. In the first transaction, the portion of Olam Haba was only "worth" one ruble. After, when the rich man was trying to buy it back, it was worth so much more. It was all based on the value to the owner. In the beginning, Esav was willing to sell his birthright for only a bowl of soup. The Chumash says that he "despised" it. Afterwards, he seemed to value it a lot more and was angry that he no longer had it.