If he ran for 2k yards and didn't skip a beat, what type of contract would he be looking at?
See, making these what if arguments are pretty easy.
That's really not the point. You and many others have argued that he was essentially guaranteed $14.5 million AND a big contract as a free agent. But that is not automatically the case. Since you didn't answer my question, I will take a stab at it.
Bell coming back and suffering a catastrophic injury late in the year would not have been that surprising given he had no training camp, was not in game shape, and probably would have been asked to be a bell cow again. If he had suffered such an injury in December, that would have put his entire 2019 season at risk. He would have been lucky to get a one year, $6 million prove it deal that had only a $1 or 2 million guaranteed. Who knows if he would even have gotten on the field for 2019 at all (and thus been in the same situation for 2020). At that point, he'd be looking for a long-term deal not having played for 2 seasons at age 28.
Don't say it doesn't ever happen. Jamaal Charles found himself in that same exact situation at age 30, went on to make only $2.3 million dollars combined from two other teams, and washed out of the league. I'm pretty sure Charles wished he held out after having producing almost 3,200 YFS and 33 total TD in 2013-2014. He struggled to stay on the field for 4 more seasons and made an average of $3 million in those years.
So in my example, Bell would have earned $14.5 million last year, $6 million this year, and MAYBE $5 million next year possible from a third team. Call it $25 million for 2018-19-20 had he suffered a gruesome injury last year. I would bet Bell will get more than that in guaranteed money next week and will end up making far more combined for 2018-19-20 than that $25 million injury projection number.
That's the rationale for why he did what he did . . . even if others think he left lots of money on the table by not playing last year.
As for your example, had Bell rushed for 2k yards, PIT could have tagged him again and potentially we would be in the same situation as last year all over again. Except the chances of Bell getting injured would have multiplied times 400 carries plus whatever he would have accumulated had the Steelers made the playoffs.
The only fact in the equation that you referenced (punting on $14.5 million last year) will soon have another fact . . . whatever he gets guaranteed next week. If that number is greater than $14.5 million, than he will have made more than if he risked playing at all last season (even if he remained healthy). That's not saying he couldn't have made a lot more had he stayed healthy, but the "fact" would be that he made more than $14.5 million.