"Conversions" on reviews are weird.

Dwarf Fortress has 28800 reviews on steam right now. A year ago they announced a million sales. So ~3%. (Using them since I knew they had said SOMETHING about sale numbers. Other games have too but I couldn't recall them.)

For that 150k/1m = ~1.5%. (And thats just 1 category, if 1-4 stars had the same itd be like 8% of purchases left a review).

1-3% is pretty usual from my understanding, unless the thing has some sort of motivation to review. (Like a good game, or a bad book.)