Cheapest I have seen so far for a GP90, the usual price on eBay or Aliexpress is around $200.
I bought one of these previously and seems to be okay for the occasional use so far. The projector has native 720p resolution with reasonable, but not great, colours. Image is reasonably sharp once focused, there is no throw adjustment though. Brightness-wise, it's not the brightest and the brightness and contrast specs are definitely inflated. Having said that, it is still usable during the day with blinds closed and ceiling light switched on. The exhaust fans are quite loud.
Not the best projector, but not bad for less than $80 shipped. There are also a few threads on the GP90 here on Ozbargain.
So what your telling me… is this will light fire and burn the house down…