I'm not a "diamond lounge customer" but I've heard the one at Harrah's is okay. I've used the one at Caesars only because of the computers there -- but honestly I haven't been to the diamond lounge in over a year.

Every restaurant is priced higher than what you would find outside of a casino. They are priced for the captive audience. However, you are buying your meal with RCs and that's a lot better than spending actual cash at a restaurant that's not in a casino.

I'll give you some prices that you would expect to pay for two people without drinks and tips (I don't drink):

Old Homestead Steakhouse $200+
Nobu $160+
Mesa Grill, Bobby Flay $150+
Steak at Paris $160+
Caesars Buffet $60+

You can also use RCs to pay for room service.