I got a MpMan 827 Android tablet for cheap (60 €) but it was Android 2.3 Gingerbread only.
MpMan 827 is just another name for the Coby Kyros 8127, or MID8127, and Coby Germany released Android 4.1 Jelly Bean for this one.
Granted you cheat a bit with the serial number (took 101110010XXX with 3 last digits being the real ones from the back of the tablet), it is an easy upgrade from their website.
I could then install Google Play following an easy tutorial.
Unfortunately, the OS is quite unstable : wifi drops, freezes and reboots are not uncommon. I tried several tricks, such as installing SoftLocker to disable sleep when screen is turned off (in an attempt to keep wifi running). Also tried Auto Airplane Mode as suggested on a forum (which should turn off wifi when screen is turned off, and on again) to no avail. It doesn't work!
I'll backup the entire system then switch back to Android 2.3 using a custom rom. It is reported to be a bit ugly but very stable.
Some users are still trying to keep on with Android 4.1 but I've enough!
Stay tuned!