Mark didn't owe Jack anything. He made it possible for him to live the life of a rock star for a couple of months, and Jack seems to have enjoyed that a lot. Great, but why should that oblige him to anything more? If you get a plumber to fix your bathroom, and he does a great job, you say thanks a lot and pay him. And that's it. No obligation to hire the same plumber again for your next, totally different project.
These kind of blanket statements make me laugh. You think being the second guitarist in Dire Straits is similar to a plumber fixing a bathroom?
Like most aspects of life, the truth probably lies somewhere in the middle, both viewpoints (Mark and Jack's) have some legitimacy.
Jack and Mark were good friends before Jack joined Dire Straits. I assume Jack thought the friendship was bigger than the band gig and would continue into the future. It didn't. I think it's reasonable forJack to be disappointed and sad about that.
All the players on the BIA tour committed to the project for many months and contributed to the successor that tour (and resultant album sales).
So why is it that Terry and Jack were dumped for the 'On Every Street' tour? I think they both had reasonable cause to feel cheated.
At the same time, yes, having paid Terry and Jack for their work up to the end of BIA, Mark had no further obligation to them. But bands and the creative people in them have more going on mentally and emotionally than a days work fixing a bathroom.