Three-toed sloths are comparable to Pandas and Koalas because they also eat a very limited list of plants. However, when it comes to crowd pleasing and attracting, I think Koalas and Pandas are a bit higher on the list. Sloths are appreciated but definitely not as much.
How much it costs, I have no idea. Maybe not that much if you manage to plant the specific species required to feed them. But it's definitely way easier to feed two-toed sloths.
Eucalyptus and Bamboos are now planted all over the world, many zoos plant their own bamboo. There is probably someone here in Europe that specialises in Eucalyptus as well, probably selling to many of the zoos who keep Koalas.
However, as the demand for Cecropia leaves is probably very low to non existent as I'm not aware of any three-toad sloth outside of its range (except in DWA) publicly kept, either you make you grow your own Cecropia, either you import it on a regular basis.