it'd make you want to puke. Aerospace systems, especially government ones, are absurdly expensive. Developing a new space surveillance radar system can easily run over $500 million. I know of more than one military communications satellite program that runs into the billions (and one in particular costs a billion dollars EACH) and these are just commsats. Aerospace systems from simple private planes through spacecraft cost far more than most people understand.

There is really no economy of scale for most space systems. The numbers produced are so small as to negate any justification for mass production, so virtually everything is custom made. Off hand, the largest satellite constellation ever made was probably Iridium, and they build less than 100 of them. Most satellites are still hand made with technicians soldiering, inspecting, documenting, and testing each wire one by one.

Based on studying aerospace history for over 30 years and working in the biz, I know there's no way the $20 billion price tag even remotely resembles reality for a manned mission to Mars. NASA wants to spend upwards of $12 billion for R&D on the Orbital Space Plane, a vehicle with a mission little more advanced than Gemini. That value is insane enough, but believing you can send people all the way to Mars and back for $8 billion more is even more unrealistic.

Developing a Mars lander alone will be a huge engineering challenge, far more difficult than the Lunar Module was for Apollo (and that was an enormous challenge). The LM was designed to allow 2 men to stay on the lunar surface for up to 3 days, and it took a substancially upgraded LM to do that (Apollos 15-17). A Mars lander will need to be stronger than the LM because it has to survive reentry through the atmosphere, plus it has to endure the aerodynamic stresses of launching through that atmosphere. While the martian atmosphere is only about 1% as dense as the Earth's, it's enough of a factor as to rule out some of the weight saving techniques used for Apollo, such as mylar skins on the descent stage. It'll need a heat shield, perhaps parachutes, and a considerable amount of propellant to safely land.

You'll also have to consider what happens should they need to abort the landing. In that case, they'll need to have enough propellant to make it back to orbit. If your entire plan is contingent on them being able to get their fuel for ascent from the surface, then you have to consider the consequences of them having an emergency that rules out landing. What happens if they miss the landing site by a considerable distance as happened in Apollo 11? How would they get their propellant needed for liftoff back to the lander? One reason why aerospace vehicles, especially manned ones, cost so much is because engineers have to look at the different failure modes and try to build in ways to handle emergencies.

The Martian lander will also have to support the crew (probably 3-5 people) on the surface for weeks or months instead of a few days. It'll have to provide for living quarters or be able to carry them to the surface. It'll need lab facilities to study samples in situ as well as the ability to carry equipment such as a rover to the surface. It'll need far larger consumable supplies than Apollo, and have to be able to stand up to far more wear and tear from daily use. The LM skins in the ascent section were so thin that you could easily punch an ink pen through them. That's hardly strong enough to stand up to long term use.

To be honest, I'd be surprised if they could develop the lander alone for $20 billion, much less perform the entire mission for that cost. Adjusted for inflation, it probably cost nearly that much to develop and build the Apollo LMs. The Mars lander will be much larger, more complex, and harder to test. As we've seen recently with the MER, designs that look good on the CAD screen often don't perform as advertised when actually tested.