Watson is great and he's young (and there's nothing wrong with his contract unless off-field issues sink him). But he can try to pick a team that can win a Super Bowl in 2022 and 2023. I don't think the Eagles are that, and especially not if they give up 2-3 picks (or equivalent) for him. And that will be the price.
Panthers offer starts with the 6th pick so Eagles would have to give two just to match that.
I don't think you can compare Watson to Vick in terms of his ability to get back on the field at a high level. He's much younger (in football terms) and wasn't in jail for 21 months, just not playing in games.