[xiaoma]

I doubt this is a sustainable market; surely, all web developers can't just sell to each other. The market for web development products can only be created and paid for by having a sustainable web product market for non web developers.

This is an interesting idea to me. Why not?

The group of "all people" sell to each other and no one else. Literate people could certainly make a living selling only to other literate people. In theory, why couldn't web developers do the same if no other customers were available?

[billswift]

Sure, you could if you didn't need food, shelter, transportation, new hardware, et cetera. But since web developers DO need these things they need to sell enough to others to get the money to buy them. In international trade, this is called the import-export balance, or balance of trade.