You're right broad spectrum parasiticides usually don't get rid of tape worms. I had 2 fur babies Paki and what do you know Loki! (which later on had a million other nicknames) who gave me a hard time with warms when they were kittens. It took 5 attempts, letting time in between advised by the vet and for their digestives systems to recover and I couldn't get rid of the thing. And I started with broad spectrum parasiticide for regular worms.
The pills the vet gave me for tape worms finally worked and I don't remember them being too expensive but I do perfectly understand and can relate with how you feel or I should say fear the vet's bill (been there before)
We have pet insurance here for our cats. Once Scully got sick with something mysterious that lasted like 10 days and ended up being a really bad case of furballs in the end it all added up to about $600 and we used the insurance claim, they covered 80% of it (which is a relief) and the money came back to us in about a month. We pay about $29-30 monthly for plan 2 and the company name is Petsecure. So far they seem to be serious and I didn't have any bad experience when I needed them and the plans seem to be affordable.
I hope your Loki gets better really soon and gets rid of those warms