Sorry, but again this is an abuse of the word upgradeable.
You could do the same with many other laptops and even some phones out there - buy from a 3rd party who has resoldered the corresponding parts. The replaceable modules brought you nothing.
Even the economic motive you mention is actually just because Apple overcharges for storage, and has nothing to do with the replaceable modules. As long as there is no cheap 3rd party source of these, a replacement module ecosystem makes no economic sense (someone will always have to bring in his device for resoldering, or you lose the price of one good working base model).