It's like buying a car. The moment your Mac walks out of the store, the ghost of Steve Jobs comes and personally curses it to 2/3 of its value that very instant.

Except with cars, that loss is against the sticker price. So if you get a good enough deal on your new car, it can in fact lose nothing when you drive it away (I got close to 1/3 off a new car in 2018, using a web-based buying agent, in the UK).

It's very hard to get anything like that much off a Mac, since Apple appears to have pretty tight control over prices, even as charged by third parties.