The article seemed riddled with errors or incorrect assumptions.
First Neil Armstrong's autograph is not rare, there are untold thousands out there. Also when is the last time you have seen even a flawless example sell for five figures? I have seen the value of his autographs dropping the last year not rising. There was a very nice unfaded inscribed signed photo that just sold on eBay for about $900.
Yes the flags carried on Apollo 11 might increase in value as well as some other truly rare artifacts like the flown checklists. I am not a Robbins collector so I have not been following their prices, but it does seem that Gemini flown Fliteline medallions have gone down in price lately. Flown flags from other missions have also dropped considerably in the past couple of years.
As our original astronauts age and pare down their items, we may see more of the same. Al Worden's flown Apollo 15 flags have been sold under $1000. Most of us know what Jim McDivitt's flown Gemini and Apollo flags sold for on Astronaut Central.
Yes, the amount of material is finite, but that has been the case since the end of the Apollo program, the difference is, I think, we will see more of them available as more of the people these were gifted to either sell them, or pass away and the estate sells them. My least favorite forum here is the Space Explorers and Workers. I have this current of dread every time I see a new red dot there as we lose someone else.
More collections seem to be coming up for sale. If this trend continues it will drive down prices further. As our generation ages and with the lack of interest from younger generations continues, I see prices falling, not rising. Already autographs of the shuttle astronauts, of course with some exceptions, have fallen quite a bit. I am seeing more sell in the $5-$10 range.
With little driving interest in the program as well as shutdown of the shuttle, I don't see it as prime investment. Maybe when we go back to the moon or Mars, we will see a resurgence.
Unless you afford to buy some of the truly rare pieces like a flag flown to the lunar surface on Apollo 11, or other missions, don't buy as an investment. Buy because it is what interests you, what you have a passion for. Buy it for what it means for you.