obviously not, and of course i never said this. point is that you can't never sell pjanic for 60m without taking an expensive counterparty yourself
what is illegal is the overvaluation of your own assets. that applies to all industries, be it manufacturing, service, chemical industry, or sports. as a bicycle rental service you can buy 30 bikes of $500 each, but you can't account them as $5000 bikes individually, cause that would make your business look like more valuable. same applies for sports.
straight out sales: the consideration is money. you found a dumb buyer, good for you. chelsea were stupid enough to overpay for both lukaku and casadei, good for inda. what's pedri's release clause? 1bn? not that it would happen, but let's suppose it does. if chelsea pay that one too, will the case get investigated? barcelona won't, chelsea might break ffp with a transfer like that. but as far as plusvalenza goes, if you receive cash, nothing to see here.
swaps: you can inflate the value of your assets, see pjanic-arthur swap, or the four fuckers included in the osimhen deal. still can't be labeled illegal by any jury (since there's no objective price list for footballers), but can be easily attacked. also it's dumb to overcharge your budget with amortization even if it's a non cash expense.
bottom line is that overvalued swaps would be illegal if there was an objective way to value a player. it's illegal for businesses to either under- or overvalue assets. i worked in a few similar cases locally with industrial companies and it can get nasty on court. but thing is that most mechanical parts, raw materials, services (etc) have more or less objective market prices. footballers don't.