The test strips are expensive. I seem to remember always hearing that they were around $5 per strip, so $105 for 25 seems like a bit of a bargain.
I stick to my reliable nurseries to avoid the worry of testing or, worse, finding HVX in my yard. I have a local nursery that was always a favorite of mine until, a couple years ago, I asked them where they got their hostas and whether the hostas were tested for HVX. The nurseryman I chatted with said, "Oh, I think that's pretty much been wiped out." He told me he had no clue about testing, but that some of their plants came from Walter's, but others came from Holland. I haven't purchased a hosta there since, just to be on the safe side.