Did you read what I wrote?
I know two people claiming PIC can be legal under FAA regulations. I think I was clear with that. However, it is not under EASA regulations and you wouldn't have 100 hours of EASA legal PIC you need to get an EASA CPL. Yes, you'll probably get away with it. However, it's certainly not advisable.
I note as well you never said whether you were paying for this person to be in the plane for 15 hours. Even for a cheap FI (CFI in American talk), that's going to add up.
And 99% of American CFIs are counting up their hours to 1500. I really can't see him/ her sat there not logging those hours. It would be extraordinary in fact.
You can get €130 in several countries. Yes, Poland, but also Hungary, Czech Republic, Croatia, France, Spain etc. I am sure there are more. Accommodation in Europe also tends to be a lot cheaper than Florida - though you did get an unusually good deal.
You can fly over many of the beaches at famous resorts in Europe at 500ft. Not just random ones. Marbella is one example.
I hadn't flown for two years when I did the bulk of my hour building (SEP was still valid though). I did 3 hours with an instructor and thought it was sufficient. That was in a totally different country and airspace setup to where I did my PPL/ some HB and was on a type of plane I'd never flown before.
Though each to their own. Glad you enjoyed it.