First a story that was told to me in my aerospace avionics class by an 80+ year old retired guy. I forget the name of the company or the person but it was my professor's friend. Anyway for the Apollo program they had to use circuit boards and resistors and transistors. At the time the average useful life of the best stuff available was like three days. Apollo missions were up to 12 days. I believe my professor's friend owned a transistor factory. Anyway he was the head of the company and got the contract for the transistors and did those batches by hand. Apparently he had trouble sleeping during the missions because the chance that all of the parts he had cooked in the furnace worked for the whole mission was very low. Fortunately, there was never a problem. So the space program forced engineers to make more reliable components that benefit us today in every electronic device we use.
Nasa has required things that are smaller and lighter, mostly electronic things. They have not always come up with the innovation itself but required that some innovative piece be used. For example, the shuttle landing strip and shuttle tires. The landing strip is, I believe, the flattest landing strip in the world. It is also made of a very rough surface so that it can move water off of it faster than any other "road" in the world. This creates an issue when you have a spacecraft landing at very high speeds on only a handful of tires. The tires for the shuttle had to be very advanced. Things we take for granted in our tires in the teens (2010s) were not really existent 35 years ago when the shuttle was being designed. Now we have wires and many layers and tires that just keep going.
Other inventions they have at least helped create are water filters, cordless tools, and memory foam. NASA has contributed to over 6,300 patents, and you can bet most of them are the useful kind of patents.
We must also remember that communications and weather satellites bring in money directly because of the information that they transmit. Talking on a satellite phone costs around $1.00 per minute, yet tens of thousands of people use satellite phones every year.
Now the future is much more interesting. I can only imagine that the technology innovations will continue to keep coming (unless Apple and Google have a war for the world's technology). However the interesting postulate is about what the future holds. Space tourism? That's a really big question. There are only a few thousand people in the world that can currently afford to go into orbit. There are probably a million or so that can afford to take a flight into "space" at 100km above sea level and enjoy a few uninterrupted minutes of free fall (weightlessness). That is unless we can figure out some way to get to orbit without traditional liquid fuel rockets (yeah... that's not happening this decade) which are very very expensive.
Another possibility is mining. Almost every 90s space video game hinted at mining colonies, as well as Star Wars, Avatar, and other fantasy media content. They were somewhat right. If we can find something (paladium, platinum, uranium, lutetium, and other rare earth elements) on Mars that we run out of on Earth then it may become economical to mine on other celestial bodies.
One somewhat far fetched possibility, yet one that people like me sit around and talk about, is the possibility that Earth by itself is not enough. We have too much waste. What if we could dump it all on Mars for only three times the price of driving it to Michigan? What if all of our mining occurred in space? What if we could terraform Mars (think Dubai meets Army Corp of Engineers) so that it was a giant recycling center. Biodegrading waste and making oxygen, yet still harsh enough that we couldn't live there without spacesuits. How cool would that be to get a three year assignment to Mars? Kind of like the south pole, but it's Mars.
I can't quote a number and say if you pay X you will get Y. Unfortunately, I think that one of the most lucrative aspects of space is the exploration itself. I doubt Columbus, Cortez, Shackelton, Admundsen, or Armstrong will be forgotten soon. So there is always the speaking tours, the book deal, the movie, action figures, conferences and the like. To quote Pawn Stars, "the problem with one of a kind items is that you can't compare it to the last one you sold." I'll translate that to mean you just do not know the end result and the profitable tangents when you try something new.