Close to lowest ever price for this well rated projector. It's ~4 years old, but still holds its ground. Cheapest 4k, I reckon, at least in this brightness class.
https://www.rtings.com/projector/reviews/viewsonic/px701-4k 6.8/10 on Rtings
The ViewSonic PX701-4K is a 4k HDR projector primarily marketed for gaming. It has two HDMI 2.0 ports, both capable of either 4k @ 60Hz or 1080p @ 240Hz. The projector also comes with an Ultra-Fast Input option promising input lag as low as 4.2ms. The projector has auto vertical keystone technology to eliminate trapezoid effects when installed at an angle and an advanced projection warping tool that corrects distorted images when they're projected on a curved surface. Depending on the selected picture mode, its light source is rated for anywhere from 6,000 to 20,000 hours. Finally, it has an integrated 10W speaker.
The ViewSonic PX701-4K is alright for watching movies. Its native contrast is great, and its brightness is decent, leading to a good viewing experience in a dark room. Unfortunately, the projector drops the ball when it comes to color, as its colors are dim, its color gamut isn't very wide, and its color accuracy is wildly inaccurate out of the box. You can barely improve it with calibration.
Free ,price in title please .