Not a straight forward answer because we no longer live in a world in which you are either a boardgamer or a figure gamer, the huge sales in GMT’s Commands and Colours system attests to that, as do the fact that gridded games for figures have become commercially viable with rules like To the Strongest. People are increasingly doing both.
Of interest is the French Vae Victis magazine. It is a wargame magazine with a boardgame in it. the first half of the mag is committed to boardgames, the second half to figures and it remains a fully viable magazine with a shared audience of interests.
I know that a figures based set of rules recently sold out of a 3000 set print run after 5 years and there is enough potential for a reprint.
Boardgames are often run on p500 / kickstarter schemes, so 1000 supporters could easily see a fully commercial print run of 1000 – 2000 games and these often go into reprints.
Another important factor is that the number of different and new boardgame designs published each year significantly towers over the number of printed rule sets, so that total represents high volume sales, though shared across many titles.
40 years ago, Avalon Hill could easily shift print run of 30,000 and the likes of basics quad leader and Panzerblitz hit the 100,000 mark.
You can’t even use magazine sales any more to gauge gamer numbers as so many it seems have abandoned magazines, being able to get free content night after night on the internet.
At their peak in the early 80’s the S&T magazine that included a boardgame in each issue was circulating as a bi-monthly at around 35,000 copies.
I did read somewhere that Covid had increased the crossover in gamer interest as the boardgame offers a small footprint game for big battles and many of the titles play well as solo games.
I have collections of both.