My memory may not be what it could be, but it seems to me that when I started buying sheets for myself many, many years ago, you pretty much had a choice of 180 thread count or 200 thread count.
At the time, my mother was thinking that the invention of no-iron percale sheets was the greatest thing since sliced bread--maybe even perforated toilet paper. She just shook her head at my insistence on 100% cotton, knowing, I'm sure that I wasn't going to be a maniac about ironing them.
Oh, but I do remember how crisp and cool those sheets were. They just got smoother with washing, but not so soft that they lost that crisp coolness.
I just can't seem to find sheets like that anymore. Now 200 thread count sheets are the bottom of the barrel. I couldn't stand the smirks of the clerks at the store if I purchased less that 400 thread count. I still go for the 100% cotton, but they are not crisp. To me they feel soft, but kind of nubby. I find it annoying. I don't have particularly sensitive skin, yet I find sheets these days irritating. They seem to have the feel of those tee-shirt knit sheets which, sorry Oprah, I just hate.
I keep going for the next price level up, but I still keep being disappointed. I probably had my first sheets for at least twenty years. Now I find myself getting rid of them after two or three years and then not liking the replacements either.
Please, don't anybody suggest flannel, fleece, or satin. Otherwise, I'll remain open minded. Maybe I should sleep standing up.