I've been hesitating to invest in SC for a long time. But then, when I learned about melting, upgrades and grey market, I suddenly realized that SC ships and store credits are equivalents to Lego sets and bricks.
I used to play with Lego a lot when I was young -- this was probably one of the factors that influenced me to become an engineer. I've been usually playing with a newly purchased set for a while, then disassembling it and adding all new bricks to the growing collection of parts, so I could build something completely new, bigger, and better.
So, buying a new set was expensive as hell, however it wasn't just a new toy that would eventually end in some bin overflown with hundreds of other old toys -- I could "melt" it at any time and use its parts with the parts coming from other sets to build a new thing. This is how I see SC ships and melting procedure. You can buy a new "set", but you can "disassemble" it at (theoretically) any time, and use its "parts" to acquire new "set". You can even sell everything on the grey market when you're done with SC or when your wife finds out how much did you spend on the game.
/ One of my last creations (2008) based on 8275; remote controlled, 4 motors, independent suspension, led lights...