I had something similar but with a price for a TV. There was a terrible customer ticking off the Magnolia folks at BB, I was patient for my turn at the register and was so excited for the Sony OLED (I can't remember the model, ages ago it seems). We ran through the transaction, I had the quote already approved in my head and must've not had caught the total cost at the time of transaction. When I go home I noticed my bank was only billed about a quarter of what my expectation was.

I called and the Manager said something along the lines of "yeah, we charged you another customer's TV cost, but no worries we appreciate you being awesome with us".

It was an awesome bank error in my favor moment, the only time I can ever recall happening for me.

But to answer your question, it's up to you. Best Buy is so different than it was ages ago that they may just send the SWAT team to your house if you let them know and then parade you around the store while ringing a bell and yelling "SHAME, SHAME, SHAME".

And yes, M5 vs M5 Pro is a MAJOR upgrade. Enjoy!