They all cheat essentially, it's the subtelty of interpreting the complex rules that separates the winners from the losers. The difference here seems to be that Red Bull simply hired a rubbish accounting team and therefore they stupidly submitted an overspend. But even in that, they are claiming they interpreted the rules on what is and what is not included in the spend cap differently from others. So they are even cheating with their catering.
The cap itself is a good thing as it serves to tighten the field and gives the smaller teams a chance to compete. But what's a cap if you don't get punished for breaching it?
As Toto has said, if the punishment is purely financial then Mercedes will breach the cap and pay the fines. Winning is more important than ethics.
I expect Red Bull will have points deducted from this years' constructors championship, a decent sized fine and a reduction in wind tunnel development for next year. This should give Mercedes and Ferrari the wee edge they need to close the gap and make next year more exciting. I don't see the FIA opening sore wounds from last year, or effecting this year's driver's championship where Max was clearly in a league of his own, overspend or not. But they should apply measures which aim to tighten the field and make next year closer. If they do deduct contructor's points, this will also affect prize money and further punish RB financially, regardless of them having a seemingly bottomless pit of money from that horrible energy drink **** that they peddle to teenagers.
Controversy is never far behind F1, it's always been that way. I bet Toto, Binotto, Zak Brown etc are shouting to anyone who will listen while also secretly hoping nobody finds out what they did to cheat...