You signed the contract that said “you get paid X amount for Y work or better.” If you do Y+1, then obviously you get paid X. There was no clause on the contrac

You signed the contract that said “you get paid X amount for Y work or better.” If you do Y+1, then obviously you get paid X. There was no clause on the contract you signed that you got paid proportional to your work, only that you got paid for doing a bare minimum of work or better. If you believe you should be paid proportional to your work, then do freelancing or have your own company. Just don’t cry over a contract you willingly signed and didn’t read.