Unsoldering the ram chips and replacing them takes some effort and skill, and then you end up paying for 2 sets of ram chips - the old ones (which you cant do anything with) and the new ones. Given the effort and cost involved, this is only worth doing if:
1) the higher ram model is heavily marked up vs the incremental component cost so buying the ram yourself is significantly cheaper.
2) the same ram is genuinely expensive, but much cheaper ram is available and still works without noticeable side effects
If it's all about markup then it's pure profiteering and screwing the users.
If the only way to undercut the official models sufficiently to make the whole operation worth doing is by using inferior components then there is *some* legitimacy to trying to stop this, but the approach is wrong.
If someone is going to the effort of replacing the ram chips with something inferior to resell the unit then they're not going to think twice about shipping with an old bootloader either, or modifying the bootloader to bypass the check, or working out how to get the bootloader from the genuine larger ram models to work on the lower ram models etc.
Sure the hacked/old bootloader might get noticed later if someone tries to update it and bricks the device, but low quality ram or a poor soldering job could just as easily brick the device too. By the time this happens the seller will be long gone anyway.
This DOES hinder repairs. For instance you might have multiple faulty units with different faults so you take the working RAM from unit A which has a faulty CPU, and switch it onto unit B which had bad ram.