Productivity growth is normal-ish, but the amount you prices have been all over the place throughout history.
Deflation should be the natural order of things; for example the unit real cost of food had gone down massively since the first half of the 20th century, which is a huge part of why people don't starve to death during recessions anymore.
Yes, and it is, for existing unchanging things. But as productivity grows we invent and buy new and improved things.
A lot of economic activity is adversarial and negative-sum. In the best case it's negative-sum but a multiplier of over 1, like police work. In the worst case it's value-destroying Uber vs Lyft wars, where companies spend on guns to fight each other with, which effort is forever lost for butter. Digital marketers are the soldiers in these battles, along with lawyers and security people.
In other words, just because everyone's rich doesn't mean there won't be someone willing to pay a lot of money to get more of the pie. Which leads to good scarcity (both from a smaller overall pie and the public having less access to it) and more money flying around, and boom, inflation.
We are in this situation today.
I do not think it makes sense to insist that money can only ever be subjective based on the possibility that transients can occur - eg a factory burning down does cause natural price inflation, but this is an exception rather than the rule.
Except in health care, education, and real-estate - all three of which are needs more fundamental than personal computing or electronics.
It's worth pointing out that this is not "weird", but rather the natural state of things! The effect is so strong in computing that we still see it, but technological progress means everything in general gets easier to produce.
This policy that "prices must always go up" is itself the aberration, instituted to keep the plebs working "full time" and to undermine their ability to save.