I paid double that last year for a used seat and backrest. I mainly wanted the backrest, but I found it more comfortable than stock. It probably doubles my seat time before needing a break. I wish it didn't lower the seating position, but I can live with that so far.
I like being able to take it off when not needed. It also makes a good backstop for strapping down a bag, or a better place to secure something on my rack.