I've been shopping around for beneficial nematodes this year. I dug out the instructions from the brand I bought a couple of years ago - ANTidote - meant to cover about 8000 square feet and it cost around $20. But the seller, Gulf Coast Biological Controls in Huntsville, TX, seems to be out of touch as far as getting these nematodes this year.
I checked at Marshall Grain in Fort Worth - they couldn't get the ANTidote so now have a brand called Orcon that doesn't have as many organisms per package and doesn't cover as large an area. And costs a lot more. 2000 sf of coverage costs $28. It looks like another organic solution has gotten the popular retail treatment. I find places online that sell larger quantities but by the time you pay shipping it comes out about the same. And those online places offer no assurance, they don't even suggest that they might be keeping these in a cold place until they ship.
Someone earlier suggested
Arbico Organics. They have a number of products that they keep cold and they ship fast, but two-day shipping now in warm weather will push the price up.
Still, they do so much good in the garden, I'll bite the bullet and buy the bugs!