A couple of things. In Bell's mind, his worst case scenario was playing this year for $14.5 million, getting severely hurt, and never getting another contract. Granted, if he took the deals offered him last year or this year, he probably would have fared better than only the $14.5 million (but that's water under the bridge).
Some team with a ton of cap room will give him a boatload of money still. If he gets what Gurley got (that may or may not be realistic), then he would get a $21 million signing bonus, another $24 million in guarantees, with a total contract of 4 years for $57.5 million.
Bell apparently doesn't look at things as never being able to recoup $14.5 million (if he doesn't play at all this season). He looks at is as ensuring he gets $45 million next year instead. We don't know what ultimately he will see in guaranteed money, but there should still be teams interested in him (NYJ, OAK, IND, BAL, MIA, CLE, GB, BUF, HOU, etc.).
So we Average Joe's will say he lost out on $14.5 million that he will never see, but he will look at it as gaining way more than the $14.5 million. And neither side would be able to prove they were right or wrong.