Lookee what he can do! He wants a job!
Sure, that is one reason Waste has a cost on it even though you would never buy one, although there is nothing in the rules to prevent you from doing so.
Well, except for the last sentence on page 7 (Trains) or the last sentence of the first section of page 7 (Rising Sun):
The rules, on Page 7 wrote:
If a card’s stack in the Supply has run out, you can’t buy those anymore because… well… they’re not there. Also, you can never buy Waste cards.