I'm a single male, late 20's and I consider myself a budget traveller.
My budget is 800 baht a night. I always try to shoot for 600 baht a night. That usually gets me a room with hot water, sit down toilet, air conditioner, TV and American breakfast. If I really want to splurge, 1200 baht is about my limit. I usually stay around On Nut or further east. The BTS extension hasn't opened yet, so the guesthouses are still cheap.
It seems strange to me to visit the far east and then just stay at an American hotel. When you are in those expensive hotels, do you even feel like you are in Thailand? Can you watch Thai TV? Is the food good, or do you have to leave the hotel to get real Thai food?
With the horrible dollar, I just stayed at an apartment for my last trip. My buddy got me in at a place that cost 6000 baht plus electricity for 2 weeks.
I've never tried one of those Home Stays, but I will probably give that a shot sometime.
I just don't see the value in staying in a $100 a night four star hotel in Thailand.