I don't think it's that short if you factor in the completion aspect. Getting both endings took me 7 hours, and completing will probably be another 12 if I choose to go that route.
For $25 I don't think it's that bad, but I'm pretty biased in preference of quality to quantity.
Took me 12 hours for the price of a couple of beers, from that perspective, sure enough bang for your buck.
However I got both endings at basically the same time so that was a bit of a bummer.
Sure getting everything to 100% would take a bit more but it's just sort of a grind (though I guess that's where the fishing aspect of it comes into play).
I did love the atmosphere and the overall theme, I guess I was just surprised that it sets you up for this dark mysterious world and then it sort of fizzles.
For the price point compare with either Loathing game (actually I think those were 25$ together so maybe compare with both). There is more content there overall.
That being said, I stand by my initial statement that Dredge is a great game and do recommend to anybody that might be interested in horror fishing to get it.