Basically, the practically the entirety of the NASA budget has to be a fake, with all the highest people (at least) at NASA HQ in on the conspiracy. What fraction of what NASA does is fake? Is any of it real?
Not only NASA, think of all the contractors that build and design stuff for NASA and supply computers, software, etc. IBM, Boeing, Lockheed, etc. as well as smaller specialist companies that supply hardware and software. When they design rocket engines, embedded computers, software systems, cameras, etc. for Curiosity, New Horizons, Dawn, Cassini, Voyager, etc., are they in on the conspiracy or have NASA effectively hoodwinked them into building a bunch of stuff that never gets used while NASA simply falsifies all the photographs and science data that that supposedly would have been collected and sent by those systems?
Does the conspiracy go as far back as the probes and landers from the 1960s and 1970s? The Mariner probes, Voyager probes, Pioneer probes, Viking landers, etc.
I presume the European Space Agency must be in on the conspiracy as well as some of these missions are joint ventures with ESA supplying some of the onboard equipment and experiments and the ESA have their own Mars orbiter, Mars Express, still active and gathering data.
As with most silly conspiracy theories, the more you actually think about it, the stupider and more far reaching it gets until it reaches ludicrous levels.