TVs are actually one of the few remaining items that don't seem to have gone up in price over the years. Gold, guns, and ammunition on the other hand are getting rather pricey.
They are basing them off of a individual's most recent tax return. So if you made less in 2020 than in 2019 you should file for 2020 immediately (if you haven't already).
It's not just ARs. Gun prices in general have fallen off a cliff due to too many being manufactured relative to the existing demand. I bought my first AR back in 1999 for hundreds of dollars more than a similar rifle can be purchased for today,; and that isn't even taking into account...