40 dollars was definitely a bit too steep of a price when you consider how the demand for pure puzzle games just doesn't seem to be there really. Because the witness is exactly that, it's a pure puzzle game.
That's not to say the game isn't incredible, there are tons of total head scratchers, and you will obsess over puzzles you can't solve and some of them are insanely well put together.
But the game has no overarching narrative really.
The game has lots of dead end puzzles that are just kind of there and don't seem to do anything in the world besides exist to be solved and then forgotten as they don't tie into anything.
And most importantly (this isn't necessarily a bad thing) most of the rewards for solving a puzzle in the game are either more puzzles or just the satisfaction of solving a puzzle.
Occasionally you unlock a shortcut but that's the most tangible reward you get.
You don't get shiny new equipment, you don't get cool dialogue or story as a reward, you're not rewarded with some visual spectacle or changing scenery, you don't really even unlock new areas (just more progress in the current one) as you can go almost anywhere at any time.
Because of those things it really does feel like a 40 dollar puzzle book, and that's something I feel most people other than puzzle game aficionados aren't exactly willing to drop 40 dollars on no matter how excellently designed it is.
On top of that the talos principle (another 40 dollar puzzle game) has been out for a little over a year and has sold about 450k copies on steam. Which is what i'm guessing the witness is gonna hit after a year with a few sales and stuff.
Basically if you ask me, the witness is doing exactly as well as anyone should have expected it to do regardless of pirates or not.