Diablo 2 LoD costed about 40$ (if you calculate the inflation cost since it went out). They had the same number of content..
It was just under $30, and that was for a physical edition. I remember this quite clearly, since I was really happy to get it from free by publisher and that I wouldn't have bought it otherwise. Got it for free cause I had to write a test for a website I was kind of working on at this time, publishers were very friendly with reviewing website in these days and sent out tons of free games even to sites not having a really high traffic (and this even if you said their games were terrible).
I already found it to be a bit too much for an expansion at this time, so $40 for a digital version ? I'm 100% sure I won't get it (oh, well, there's also the slight detail that I won't have a real computer, or maybe no computer at all, for the year to come and maybe more that makes this sure).