This is a really high(shocking even) number and would explain a lot.
Yep! DLSite takes a pretty penny for sure, but it's worth it for the extra reach to foreign markets. If you're curious, you can take a look at their pricing model here: http://www.cf-dist.com/
So as that page says, selling the game at 1000yen nets me 450yen after DLSite/CuriousFactory take their cut. I'd like to put it up for cheaper, but any lower and the percentage I get becomes smaller and smaller, and idk I already kinda dislike having a minority share of the profits as is.
Needless to say, I definitely try to encourage people to purchase my stuff here lol