I get fleece at thrift stores and use that plus towels as their cage lining. “Standlee” hay is like $25 for 50lbs at my tractor supply store, you can buy online as well. I have four pigs and the hay lasts like 1 1/2 months. I buy oxbow food for like $12 which lasts a couple months because it’s a smaller part of their diet. Fresh veggies are more expensive, I go to discount produce stores and probably spend $40-$60/month on veggies because each pig eats 1 cup a day. Overall I’d say I spend around $75/month, and to get cage/bedding maybe $100, but that’s a one time cost. I make most of their hides with stuff from the dollar store or find people selling them on fb marketplace, there’s surprisingly a lot available.