I've seen prices for a culture and antibiotics all over the board, some are next to nothing and some (like what I paid) seem to be on the high end. I've used two different reptile vets (the one I went to first for issues then I found my new go-to exotics vet afterward) but the exams cost between $30-40 by themselves (ask if the practice offers any discounts: the vet I go to now offers a student discount and military).
Baytril ran about $20 for a months supply which (usually) kicks the RI, it seems most vets prescribe antibiotics for at least 2 weeks up to a month or more depending on the severity of the RI. You can also use the nebulized F10 in conjunction with the antibiotics also. One of the bps that came to me ill had a re-occurring RI that ending up costing over $350 to get a culture done to prescribe a different antibiotic than Baytril since Baytril doesn't always kick the RI infection depending on the strain of RI. I think this is on the high end since I've seen some get cultures done for well under that. So what to expect: expensive vet bills that can come with owning any animal! And after personal experience get a culture done first before trying any antibiotic.
On the note of expenses and vets, from personal experience I can't recommend finding a knowledgeable vet enough and don't always assume that odd behavior/physical signs are nothing to worry about. I don't want to fear monger but I've had a rough year last year in regards to snake health issues so I am very cautious now when it comes to their health and when things seem "off". One of my corns passed from pneumonia (me and the vet have no idea how this came about), one needed invasive surgery when she became egg bound after being paired two years previous with the old owner (not the most common thing ever), and the bp with the re-occurring RI that finally cleared up ended up showing odd neurological issues later on (no spider gene in him) that cost a lot in tests and treatment (found out he had an infection in his spine: me and the vet have no idea where this came from either but think it was an underlying issue to the RIs. He has since been treated and he's made a full 180 from where he was and I couldn't be happier. I am very hopeful for his future!). Sorry for the novel: I think it's just very important to expect the unexpected with any animal and be prepared to deal with it when you need to.