That is the question and their mode of business. I am not aware that they are required to perform work on random Macs brought to them and they are pretty scarce. Which brings us to point #2:

Also there is a big difference between “it can’t be done” and it “cost more than I’m willing to pay”.

Yes, it is better than "it can't be done". But it is a strong limitation of a computer, if the pure work price for exchanging a memory module or a SSD is $300. And requires to find a service center which can do the work and probably a longer stay there. Even on most laptops, such actions are a matter of a few minutes, and on most desktop even much faster and normally user-doable.