Depending on your price elasticity, it's always worth checking on the MLife Gold/ Platinum member rates at Monte Carlo as well as Luxor/Excalibur. Unlike the latter two, Monte Carlo is a true 4-star / 4-diamond, and while it's not the Aria or the Bellagio by any stretch, it's eons better than Luxor or Excalibur.

The VIP Lounge access for MLife Gold or higher is a nice bonus and it's not uncommon to see $45/night room rates at MC for mid-week or for Gold/Plat MLife member rate offers.

YMMV, but presented with $25/night+ for Excalibur or $45/night+ for MC, I'd pay the extra $20 at MC hands down every time.