The average NFL career is about 3 years (that's all players combined) but if you are more talented (PB type) or starter you're looking at a decade or more on the roster. Lineman are some of longer careered players. So you don't spend much money on someone you think is going make it 5 years at the very top of their game. He would be much better off to improve his skills and make people feel he's worth the risk. He's still a project at this point.