I was aware of him from reading about six of his novels in a little high school library on the other side of the planet some time before he wrote "Valis"
Thus I really think "millions of copies sold worldwide" trumps your "unknown" :)
First, I said "almost unknown" not "unknown". Second, prove it.
I cannot find any references to sales figures for PKD's books, but in his own words (from this interview):
...there is also the very real possibility that if I tried to do the cheapo novelization I would actually fail to do it, literally could not write a commercial novel that would be something that would sell millions of copies
That interview was done in 1981 (a year before he died), "The Man in the High Castle" was published in 1962 and it's one of his most popular and known books. If it had sold "millions of copies ... worldwide", you think he might have known about it. Sure, there's a slim chance it has sold millions since then, but I can't find any evidence of that and we are talking about "while he was alive". It seems you are making things up.
Thus, I really think my "almost unknown" statement (adequately supported, I believe you will find, by PKD's wikipedia entry) and PKD's own words trump your anecdotes and made up figures.