If Bell had gotten the $30 million guaranteed that was expected, there might have been more of a ripple effect. You could make a strong case for giving up a year & $14.5 million for a guaranteed $30 million a year later. But when you combine the only $25M he got from the Jets with the $20.5M guaranteed in 2018 he passed up by not signing the Steelers contract, he's a clear loser for holding out. He could have either played 2018 for $20.5M and still become a free agent this year (if the Steelers cut him) - or he would have received $33M for playing 18 & 19 for the Steelers.
Offer him a fair contract this off-season and lock him up for the next 5 years. If he holds out, he can't win. If he refuses to play, he'll be 365 lbs and run a 5.3 40yd before another team can even look at him.