Let's work this out:
Shuttle launch $440M for 7 people -> $63M per ticket.
Distance traveled (SS Discovery) 148Mmiles (39 flights) -> 3.8Mmiles per ticket.
Cattle class flight is about $400 LHR->SFO (5300miles) -> $0.08/mile.
So NASA is about 200 times more expensive per passenger mile*. They can probably get a higher class of waterproofing for the mark-up.
* I'm counting the flight crew as passengers as well.