I think overcharging for RAM (or HDD/SSD) upgrades is one way that OEMs make more money off of their machines. I am a bit amused that this is the reason you give for reconsidering Lenovo when Apple (the maker of your current machine) is notorious for doing this: http://www.zdnet.com/blog/hardware/just-whats-so-special-abo...
One good thing about ThinkPads is that most of them do not have their RAM soldered to their motherboards, so it is easy to buy your own RAM on NewEgg and then augment or replace the machine's original memory.