I mentioned this to someone a few minute ago and thought it might be helpful to mention to some other snake owners. Although I'm sure some breeders have other sources and this may not be the best one, somebody might find it useful...
If you're looking for a cheap supply of aspen, there's a company called Sun Seed that makes dust-free shredded aspen. It comes in a value size called the 'Press Pak 3200', it may be hard to come by in your area but they come in a variety of sizes; keep looking!. It's compressed volume is 1250 CU IN and expands to 3,125 CU IN. I get it a pet store for $11CAD. It lasts me just over 2 months for one 20 Gallon tank, regular spot cleaning and fully renewed substrate during cleaning. They normally make it for rabbits and small rodents but it's super money efficient as apposed to buying "reptile specific" substrate in a quarter of the size for similar price.
I don't know if there's any way to turn this into a sticky or something.
If you've got any other alternatives or cheap bedding sources, feel free to post/discuss them here.