If he plays well long-term he'll have left money on the table. No doubt.
But I think Taylor's willingness to sign this deal is a direct result of past (or lack of) earnings. He's 5 years into the league and hasn't sniffed his big pay day. The Bills knew this, and realized with only one above average season on his resume, TT wasn't in the position to leverage a huge payday based on past performances. In a nutshell, this mutually beneficial deal had just as much to do with last season, as it did with Tyrod being a career back up the majority of his career.