But the shuttle has to survive reentry as the navy pick it up. Otherwise that adds about 5,000 to 10,000 people. Thats a lot of money. It would be far easier for one of them to blab and make far more money than they are paid.
Also if the shuttle is destroyed each launch, that means NASA would have built 30 shuttles. Also lots of debris raining down on people. Also people can see reentries with telescopes sometimes. Also contractors would have noticed how Nasa ordered 30X the parts it needs.
See how this doesn't work? The conspiracy would be hemorrhaging money, whether you care to admit it or not.
Also it isn't much cheaper as launch involves massive acceleration just like reentry. You just need the tiles which ARE ON THE SHUTTLE. Its not like they use fake tiles. The shuttle has to survive scrutiny of scientists that expect it to work. You pretty much spend 99% of what a real one is.