As an individual, I can just by it in the US for personal use, and carry it over. But if you intent to transporting them for selling them, the story is very different.
Chances are, you aren't checked. But if you are, having the original packaging or charger will be noticed by customs. They might even have data to determine country of origin from a serial number, or notice that it's a version that wasn't available when you left for the US etc. And if they ask, the burden of proof is yours to show you bought it in the EU.
I lived there for one year, and bought a lot of stuff in the US for personal use (like clothes). When I moved back to Europe, I just moved everything with me without paying any VAT.
I was worried that they would make me pay VAT from socks and underwear to laptop, phone, and everything. Asked about it, and was told that I didn't had to pay anything.
https://ec.europa.eu/taxation_customs/business/calculation-c... (the linked PDF).
Import duties and VAT. VAT accounts for much of the price difference, OP didn't explain which Europe they're talking about, but assuming a 20% VAT a 2999 machine costs $3598.8 to the end-user.
Means you're working with a 325.2 price difference, which doesn't even cover import duties.
So pretty much as ever, if you're round-tripping through the US, picking up an MBP there is nice. It does not however make for a business.
Just keep in mind that if you stay in the US for less than 6 months, you should be paying VAT on it on your way back (see other comments). Otherwise this probably counts as tax evasion, which comes with pretty hefty fines in some EU countries.
You can change the layout in the apple store when buying it here, but that adds 4 weeks to the delivery time..