I shall probably ramble.
Firstly, hats off to the poster who mentioned why film seems expensive. Many may prefer not to believe it, but the nature of film manufacture (about which we enthusiasts often know surprisingly little) and contraction of the market mean those £2 or $2 rolls of film in the supermarket are never coming back.
Sure....20 years ago I could send a C41 film off for processing at a cost of £4.50 and get a free roll back. Or I could buy a roll of film and get it processed via a shop near work for £1.99. those were the dying days of film being the only viable image capture option for most people. Then came digital, and in particular phones...which perform all the functions that used to be done by box cameras, point & shoots and so on. There is upswing in film usage, but it is never going to be 1999 again. We need to accept that.
So with the gloom out of the way, how can you save? As others say, buy in bulk. For 35mm I generally have two or three bulk loaders going....with Fomapan 100 in one, Fomapan 200 in another and Ilford HP5+ in a third. If I wasn't shooting in a dim jazz club I'd go for Kentmere 400 instead of HP5+ but I want something I can push to "ludicrious speed". I am strictly amateur, except when someone sees one of my photos and offers to throw money at me (has happened, but I refuse to engage in pre-paid gigs). So while one can argue about the magic of film, I do this because I enjoy it. And while I am not struggling for money, nor am I in any way rich. The days of visiting Paris on EasyJet and shooting 6 rolls up the Eiffel Tower are gone. But then, frankly, only about 10 of those photos were really good anyway. I might as well have more carefully shot one roll and a bunch of digital shots.
So here's what I do. When I am running out of one of those B&W films, I shop around. I look for the best deal and buy another 50 or 100 foot bulk roll. Part of the reason why I use both Foma 100 and 200 is I'll buy which ever I can get a better deal on. I've settled on processing in Ilford ID-11 or Microphen, which are pretty cheap and still widely available. I'll buy three 1 litre kits when I see it at a reduced price. Lasts me months. Maybe 9 months or a year shooting at least a roll a week. I use Adofix fixer which comes as a powder so like the developer, postage costs are low. Again I buy a year's supply at once and it is really cheap. Yes, I could go even cheaper by going the caffenol route and mixing my own fixer as I have access to lab chemicals at work. When doing reversal work, I do actually mix dichromate bleach at work. Honestly, I shoot upwards of 80 rolls of B&W film a year and spend less than £45 on processing it.
Then there was the fact that I got lucky, or was clever. I bought my Jobo tank in 2001 when nobody wanted them and the local shop was selling them cheap. I similarly got my bulk loaders in the 2000's when film gear was being offloaded as everyone "went digital". The deals i got were frankly obscene looking at today's prices. BUT you can still get lucky on eBay or find a relative/friend who has one to spare. I've been gifted dark room equipment in the last five years by people clearing out deceased relative's houses or finding their old stuff in the attic.
If you don't mind hybrid work, then scan your own negatives. I was given an Epson flatbed scanner that handles 135 and 120. Given. But again, you can pick them up cheap on eBay etc. If you really do want to do darkroom prints (and I do occasionally, there is nothing else quite like them) I find that expired B&W paper works great. A friend found boxes of 1970s bromide paper in his deceased father's darkroom and gave them to me. I'm set for years.
For C41 colour, buy more than you need when the film is available....because supplies are sporadic. Look for deals on short dated film, especially if you're sure you'll shoot it in the next 12 months. Find a lab you like at a cost that works for you. I am lucky that for £4 I can have *any* format (110, 120, 127, 135) processed and scanned for £4 flat fee at a lab I can walk to. But that is unlikely to be the case for all. If you find a lab locally where you can actually visit and talk with the staff, that's a huge bonus as you can get almost bespoke scanning (if you wish to have scans made).
For medium format B&W, I use Fomapan mostly and buy bricks when it's short dated. I will happily use Fomapan 400 in 120 as the grain isn't intrusive as it can be in 135. For colour, I may well switch to kodak Gold but I've been using Lomography 400 and Kodak Ektar....often short dated or on sale.
Keep a look out, bid low on auction sites....expect to lose but once in a while you get lucky. Find real old style camera shops, they sometimes have expired bulk rolls. Mine had some 400 foot cine rolls of HP5+ about five years ago, found during an audit of their basement, selling them for £20 a pop. Similarly rolls of 15 exposure Agfa Vista (the real stuff) selling for £1 a go. That's lucky, very lucky, but it happens where you have a proper old camera shop that might have old stock somewhere out back.
Something else I do.....when *anyone* asks if they can buy me a small birthday or Christmas gift...I suggest film....literally *any* camera film will do. I'll find a use for it. I also occasionally get gifted expired film when people find it, and even cameras.
Just my experiences. YMMV depending on where you live, how generous your friends are, how much your national post costs and so on. But possibly some ideas.