Any good and cheap flea treatment for cats?

I’ve had my oldest cat for about 9 months, and ever since I got him, he’s had fleas. I’ve tried the back of the neck medicine, but it didn’t work. I got a new kitten the other day, and when I brought her home, she didn’t have fleas and now she does. I need a cheap flea medicine because I can’t afford Frontline or Advantage. Does anyone know a good OTC flea treatment or at least something under 50 dollars?
Thanks so much.

Advantage is under $50. You can get a 3 pack from

Yes – there’s lots of off-the-shelf crap that’s “cheap” but they’re a) mostly ineffective and b) contain harsh pesticides that can make your cat very, very sick. Why would you want to risk that?

Question – if spending $40-$50 on flea meds is “expensive” to you why did you get a cat? What happens when this cat gets very sick or injured – how will you afford that?