If that's your budget I reckon my suggestion would be to look into the better brands but used units rather than going with a new budget unit because it was less expensive (remember the old adage about getting what you pay for?)
I'd rather buy a used Kenwood/Pioneer/Alpine from a trusted source than buying a new Boss/Pyle/Jensen from anywhere, personally.
To more directly answer your question, however.......I haven't seen one personally but the only in-dash DVD w/ screen that I have seen decent reviews about is the new Jensen. I'm not sure what retail pricing would be but I would have to assume it would be less than the Alpines, Pioneers, and Kenwoods.