Should Shnaider sell? I think if he's a true business person (and I think he is) he should sell. Especially for triple the price he paid! That's damn good for F1, when considering most teams defunct.
These days, its obvious money makes a team competitive (pretty much to a good extent). If Alex isn't willing to bump up his investment into his team, let someone else do it. Otherwise, F1 will just go back to 3 teams for the glory and then best of the rest again; the last 3 years the competition is getting tighter.