Sorry, didn't see this thread earlier. Check out the prices of acrylic primers at Dick Blick, here
They're a longtime supporter of WC! so like to recommend them but they're often the cheapest of the online vendors too and have great service and shipping rates to boot.
If you're ordering anyway you may like to lay in a stock of acrylic paint
, which is also much better value when bought online compared to most stores. Blick's own-brand acrylics are definitely worth a shot and they also stock Tri-Art, probably my favourite artists' acrylics, in addition to the old standards on the American market, Liquitex and Golden.