Sonny Gray isn't 37 and won't be for a few more years.
Happ is actually less desirable than Eovaldi for a few reasons. And you know this based on the activity and contracts both got when they were competing free agents one year ago. Eovaldi's injury really doesn't change this, since it was hardly a surprise.
If the Yankees can move Happ, be happy. But they are going to eat a good chunk and probably get back very little, if anything. But the proposal on the Yankee thread was the team could move all $17mill by including some ubiquitous mediocrity like Steve Tarpley. Not going to happen. While he's a better trade target than Price, that doesn't put Happ in demand. And while the Yankees have some good pitchers on the farm, that doesn't mean teams are clamoring to get any of them to the point where they will gladly pay $17mill to any warm body coming down the pipeline with them. Want someone to take Happ's contract? Attach a real prospect. Flovial still might get the job done, but he won't if he continues down this path. Maybe Gil?
And if your selling point at any time uses the words "he could," then you don't have a selling point. We might as well have posts saying "David Price could bounce back to Cy Young form. And if he does he's a bargain." And you know what, that is a true statement. But it's not a selling point, since its not very likely.
Happ is an innings eater at this point, which even you yourself said, but in more market-friendly verbiage. He is the older (re: less durable) version of Rick Porcello. If a 30yo innings-eater is worth $10mill, a 37yo innings eater is not worth $17mill. That the price of Cole and Strasburg went up really doesn't affect the price of Happ...