You and your employer agreed on what that value of your work is prior to you completing it. So long as they do their part, it’s not wage theft any more than making a low-ball offer on something you see on Craigslist is theft of product. In either case, one party is free to refuse. Both can renegotiate from there, or either one can walk away from it all.

Correct, but, a contract was made. You agreed to work a certain amount of time doing a certain job for a certain pay. Upon completion of that work you’re paid what was agreed to in the contract.

I don’t like it either but there’s a reason it’s not illegal. Immoral, maybe, but not illegal.

Well “fair” is subjective, I was just objectively describing what is happening.