Here is an article written in 2001 that talks about some of the benefits and drawbacks of a socketed component vs a component that is soldered directly. Note that there aren't any hard numbers, but it explains WHY a socket can be an issue from a reliability standpoint.
http://www.imaps.org/journal/2001/q1/liu.pdf
Basically the benefits that are listed are all of your arguments for socketed RAM, and all of the drawbacks are my arguments for soldered RAM. There are good reasons for both, and I'm not saying upgradeability is a bad thing. I'm just saying that I place a higher value on reliability and I'm willing to accept the trade off.
I'm not arguing with you on this point. If a user wants more RAM, they'll have to pay Apple for the upgrade. If this is actually the reason why Apple has had increased profits is questionable, but it could be a contributing factor so I won't rule it out.
Soldered ram can actually be worse, while rare, ram modules can fail, and if that happens you'd have to replace entire logic board rather than simply removing faulty ram module and replacing it with a new one. Sure one can get Applecare but that only covers 3 years.
Considering both ocurrences are extremely rare, which one would you prefer though, unseated ram which you can re-seat easily or replace (socketed ram), or faulty soldered ram, which would force replacing entire logic board possibly resulting in you losing laptop if it's outside warranty?