This $40 one is only 15k at 15 degrees, so it's a very slow scanner indeed!
It is -very- cheap though if it's the real deal, and if you just want to play with it for a bit i think it would make a decent kit to test the waters a bit. There seem to be NO adjustment pots on the driver board for this cheapest version though, so any fault compensation would have be done in software. On the $100, 30k model all adjustments seam to be available on the driver board.
I would not expect the $40 set to be able to do any animation or such, but it could create nice effects like tunnels or planes at a very low price point.
It also says it's including a power supply, but i don't see that anywhere in the pictures. It may not come with a mains power supply at all and you'd need to get a +/- 24V mains supply yourself. Those aren't that expensive and can be re-used for other projects easily, but it's another factor consider.
If it comes for $40 shipped and works it'd consider it a fun unit to start out with. It will not run amazing beamshows or anything like that, but could still pull off a pretty decent show in a disco environment when used with the proper lasers. Word of warning on that though: these things are not that easy to build, especially when you want something like RGB projection. In such cases the other components will cost far far more than the $40 for this 'scanner' unit, but if you just want something entertaining to look at, probably with a single color from a cheap laser, it's worth considering.