Ask HN: Best 3D printer for an 8yr old?

My nephew is intellectually precocious, insatiably curious, nearly perfect memory, learning to read, and just on the verge of being old enough to understand and appreciate a 3D printer. However, I'm considering getting him and his parents one this Christmas anyway, more so his parents can start figuring it out, but also for early exposure for him. Who knows what he might be capable of? I think these are the PC's of his generation, still in the Apple I/II era. Given that, I'd appreciate any recommendations anyone has for an appropriately simple yet fun and interesting, not too expensive (will buy a better one when it's clear he's ready for it) 3D printer.