Except that the other melee class, Barbarian also has a boost to resistance that puts them +50%, and I think most Barbs tend to use that through inferno. Using One With Everything on a monk does help, but it means you'll have to forgo some upgrades specifically because they're not your resist. And dual resist items aren't cheap, since monks have to have them. I think using One With Everything and getting through Act 1 can be cheap, since you need a lower amount of resistances, so you could pick up something without all res and just has your res of choice for cheap, but that's just act 1. Come act 2 and 3 you need every piece to have All res and your specific one.
Monks also don't have very many dps type skills like even a Barb has, so we have to try and survive even longer while plinking away. And lastly, major dex upgrades aren't cheap, since DHs all use those, too.
Yeah, this seems pretty crazy. That's why I just dropped the healing mantra with my monk and put on evasion instead. Having over a thousand in resists meant I died in like 1 second of desecration instead of .8 seconds. I wanna know what kind of crazy resists and armor you need for that stuff....