I can't believe this is legitimate... are we sure it's legitimate????
If a "black" quaker is in actuality a mauve quaker, then the short answer is "yes"... you would need a quaker with the blue mutation, the grey factor, then double factor dark! That is, a bird with, at minimum, "5" mutations, maybe 6. (split between both chromosomes - two blue to be visual, 2 dark to be, well, dark!, and depending on grey mutation - 1 to 2 of those! depends on if mutation is recessive or dominant)
As far as I can tell, and I could be wrong, but this is a pallid grey... there is no way you are going to get a black quaker from him/her any time soon! Or ever! Not to say you can't use that bird's genetics to eventually produce a black chick after at least a couple of generations, but that bird in particular can't produce a black chick. That quaker would need a dark factor and would need to be paired with another quaker that is visually or split grey (as I understand it, grey in the USA is recessive), visually or split blue and also carries at least one dark factor. If a white quaker isn't also grey and dark factor, you will not get black chicks...
In short, $2k might be too much of an asking price for the bird.... and based on their website, you aren't even guaranteed the bird pictured.... which doesn't look to be in good feather anyway.
Perhaps I'm wrong... I don't really follow quaker mutations nor prices.
Back in the spring, a local pet store had a gray QP for $550 (already sold when I saw him). That seems like a much more reasonable price to me. 
