The prices will vary between clinics and also regional/geographic areas (it is not well known that clinics in Southland charge a lot less than clinics in Auckland. Don't know why that is, I guess they base it on higher incomes in more heavily populated areas, and what people are willing to pay or reasonably expected to pay. You could imagine from that, that Wellington is somewhere in the middle!)
We were charging about $28.70 for a bottle of Bomazeal Cat Pep. They contain 100 tablets, and it's initially something like 2 - 3 tablets/day for the first 2 - 3 weeks, then one tablet/day after that, as a maintenance dose. I could be confusing this with dogs however, so don't quote me. The Bomazeal Senior was recommended at $39.95 for 100 tablets. It pays to check (if you are looking into the Bomazeal products) if your clinic can or will order in larger size bottles, I know they come in 300's as well.
Noractive I can't remember the exact price, but I think it was somewhere between about $28 - $33 for a box (30 sachets), somewhere around $1/sachet, but remember that this is available on prescription, if your vet recommends it. It isn't OTC.
I don't know the price of SF4, we didn't sell it.
Actually I've just been browsing on the net and you can go to: Pet Post, look up Animal Health on the left hand side, then Nutritional supplements, and that gives you a huge list. The ones to look for are Bomazeal Cat Pep, McFarlane SF4 for Cats, Pet Mussel and Pet Shark. Their prices are really good too, and they offer free delivery for orders over $50. I would ask your vet first if they think that it would be beneficial.
(Having said that, I have spoken to the Bomac Rep - Bomazeal - and she told me that Cat Pep can be given simply as a nutrional supplement to boost cats, rather than an aid for helping older or arthritic cats). Hope I have helped!
As for side effects, I haven't heard of anything damaging happen to any patients, but it would pay to maybe do some further research, email Bomac Laboratories or whichever company makes the product you're interested in, or again, ask your vet. I think they're ally pretty safe.