Album sales don't matter at all. The Ramones are probably the worst selling band to be in the Hall (I'm not knocking them, of course, but they never did sell that many albums)..
And isn't Tony Basil, who did the 'Mickey' song (which was, incidently, parodied by Al), in the Hall? And she's basically only remembered for that one hit (though she has been a choreographer for other stars). I think it would be terrible if Al was not inducted whithin the next 5-10 years... he's eligible and still performing! I don't even think Van Halen is performing anymore... nor were most singers/groups when they got inducted.
Al should go in, he deserves it.