If anything, the way maintenance requirements are headed post-EASA, it will reduce its value significantly to put it on the G-reg.
Yes, funny one that.
When the DfT was going to chuck out N-reg planes, the talk was that they would lose a lot of value, and the bottom end types would end up being scrapped (uneconomical to export back to the USA).
Now that's been abandoned, this one has gone away but EASA will be pushing for something similar, so it's going to come back. OTOH the EASA maintenance regime (if implemented as proposed, and if I understand yesterday's impenetrable presentation, which I doubt) is going to make G-reg life at least as complicated as it has been previously, which (if EASA are also slow in kicking out foreign reg planes) would work the other way on N-reg values.
However, assuming private use, aircraft maintenance is not an item on which any big savings can be made, no matter how you play it.
I also don't think EASA can afford to screw EASA-reg owners that badly, otherwise the move to N-reg will speed up. FAA Part 91 maintenance is a straightforward procedure which isn't any cheaper but has very nice options to use a trusted
competent freelance A&P/IA, no need to use some CAA/EASA certified cowling screw chewing-off outfit.
And kicking out N-reg planes is politically awfully hard. The UK DfT failed (it seems like it failed very rapidly indeed but delayed the announcement for a year, to save face), France failed very rapidly too (but didn't bother to save face; they just blamed it all on a "junior official acting beyond his authority"
) and nobody else has tried it. I believe Denmark or Sweden have a law banning foreign reg for > 6 months but it clearly isn't enforced.
So the future of aircraft maintenance will be interesting, and won't pan out the way proposed, for sure. And EASA know that. I am sure they are playing a clever game. They are French after all