$0.50 seems a little high. I think mine were about $0.10 each.
With my wife's car it's a rubber gasket, so as long as the rubber is in good shape and clean I'm comfortable re-using it (sometimes lasts 3 changes).
My Del Sol had true crush washers, where it was a metal that crimped down and formed a nice seal. They DEFINITELY had to be changed every oil change.
The MO's crush washer is a little different. I'd say that in a pinch it should be fine to re-use it once, but I wouldn't want to do it less frequently than every other. I always try to have several extra crush washers on hand just in case (recently bought 8 oil filters and 12 washers).
I also like having an extra drain plug on hand as well.