Lyme sulfur dips. Am I getting ripped off?

My kitten was diagnosed with ringworm.  She's about 14-16 weeks old.  (My ex found her so we're not sure of her exact age.)  We were using a topical anti-fungal until culture results came back, and it was improving with the medication.  Once the cultures showed positive for ringworm, the vet recommended lime sulfur dips, twice weekly for 6 weeks.  At the 4 week point, they re-check cultures and if they are negative, we get to stop at 6 weeks. The total for the entire series is almost $400, not to mention each culture.  If I remember right, it seems the culture was around $50 but I'm not sure.  

I just want to know if this is necessary or if there's a less expensive solution.  I am committed to caring for this cat now that she is part of our family.  I just don't want to be taken advantage of.

Hmmm, is it lime or lyme?  Looks like I spelled it different each time.  I guess that's because I keep seeing it spelled different ways....

When my cat had ringworm as a kitten I treated him with a topical cream only and it cleared up in a few weeks. My vet recommended a shampoo for him but I decided not to use it. He only had a few little spots in the first place, though. I don't know how bad it is in your kitten's case, but if the current medication is helping, I personally would be inclined to keep using it rather than go to the expense (for you) and trauma (for the cat) of dips.