I personally don't think a $75 test is expensive in the grand scheme of things. I read the doc you linked to and they are being very nudgy for lack of a better word. You collect a full wet stool sample and put it in a bag and there will be plenty of quality poop to do a PCR test. I've collected 100's of stool samples for PCR testing and none was rejected. As for cost, vet care isn't cheap, we all know that. But whatever it costs today to test and treat this kitten, ignore it long enough and it will cost plenty more.
Ah Found it. This is what I was looking it when I was thinking about whether he should be tested. I saw that the test wasn't that expensive, but what I remembered was this that you needed a fecal loop (i.e., veterinarian) to collect it otherwise the test was relatively unreliable, That isn't mentioned in the documentation from the test manufacturer, but it is here (see page 6): http://www.cvm.ncsu.edu/docs/documents/ownersguide_tfoetus_revised_122009_final.pdf
Perhaps this is what her vet meant when he told her it would get relatively pricey to do the test. Or maybe he's not even familiar with it (never came up in the two vets I brought my cat to.)
What I was picking up on in her post was her concern about the cost, to me that's more of a barrier to treatment than people not understanding what they should do. I don't doubt that it may be apples and oranges here, it's just that a lot of people only have a choice of apples.