Real Action Heroes and Hot Toys are of much higher quality than Play Arts Kai and so warrant the high price tag. And whilst I personally quite like PAKs, they do have a reputation for having a lot of problems with QC, questionable sculpts, and less than ideal and oftentimes ugly articulation.
Not only that but they used to average around $50 - $60 and now they're closer to $100, which for what you get is not really justified a lot of the time. They're certainly not worth $250.
When they get it right they knock out of the park (the latest Master Chief is absolutely fantastic) and they have been getting better, but their rep is there for a reason.