As far as the claims about canisters, yes, they are not refillable, no, not absolutely true they are hard to find (depending on where you live, of course) and yes/no depending on your definition of expensive.

Some canister stoves are better than others. I have two- a Primus Micron and a Coleman Xtreme. The Coleman canisters are hard to find because it is not your standard canister stove, but canisters for the Primus (and similar stoves) are readily available at almost any outdoor shop and many discount retailers that sell camping gear.

While alcohol stoves are popular with UL hikers, a canister stove is about the simplist stove there is to use.