I guess it's more about convenience than cost, as it's not going to be a massive amount of them. It's not for public show really, but for having in my "studio" to look at myself and let a print mature in my mind. I'm starting to have some good work, but it's not like I'm on the virge of starting a photo gallery. I need more time, and figured that one part is to learn printing as I want that to be part of my creative process. I've done some prints before but with the help of printing services (and framing services). For permanent framing I'll probably use the local frame shop also in the future, as they'll do the craft better than me. I'm good at many things, but crafts is not one of them, so I'd like to keep it simple.
I use multiple formats today, mostly 4:3 and 5:4 though, but occassionally others too. As look is not too important I guess I could fill out the space with mat and still used one-size-fits all frames.