What happened to a person's intergrity?

Jason has just told me that the deal to buy the van is off. I am so pissed off after hearing the news. We have already made a deposit and there is a written black & white that we are buying his van for that amount! The angriest part is that he wanted to revoke his promise because someone offers him at a higher price! I am really really pissed off with him. I told Jason that actually we can sue him since there is a written agreement but Jason said it will not be too nice since they are working together. That the thing that I don't like about buying cars from our own people. Even if the person is in the wrong, what can we say...? It makes me wonder what had happened to a person's integrity. Is money a more important factor then?