The River to River trail here in Southern IL has very little to no maintenance in some of the privately owned easement areas like Power Line right of ways and privately owned areas with trail permissions. The landowners don't clear them. Some of them bought he land wth the stipulation that the R2R crosses the property, and the locals in some places seem to like to collect the blazes or use them for target practice.
The cheapest I have found them is .50 each plus shipping, and you still have to mark them. A piece of white vinyl siding I had laying around got volunteered. They are smooth on the inside and made to be UV sensitive. Some Blue Krylon plastic paint looks good enough for lost people. Not for the AT, but for any volunteer maintained trails in need of blazing (in non wilderness designated areas) its better than the rotten wood ones that are missing or falling apart, and not as cruddy looking as paint sprayed on a tree.