I don't know if the iMac is as upgradable, but when I bought my Mac Pro I just got the default amount and upgraded it with third-party RAM at a sane price.

upgradable with 4 slots - I generally buy my ram from crucial or ramjet

It's DDR3 memory and 16GB of it. Crucial has similiar prices for that.

Do you need 16GB of RAM? Seems like overkill unless you have a specific reason for needing it in which case the price probably isn't a huge concern anyway. I had 16GB in my Mac Pro until recently I downgraded to 8GB. I never came anywhere close to using 16GB and FB-DIMMS on the MP are power hogs. -30W of power yanking the extra memory.

Yea, I can understand it's expensive but the thought of spending more than what a baseline iMac costs just for RAM is a tough pill to swallow.

Their markup over wholesale prices is only around %30 -- 4gb SO-DIMMs of DDR3 cost at least $270, where 2gb sticks cost ~$40.