I think there are two things to consider here.

One is that many members of this board have bought into ebooks, so we are going to be biased towards them.

The other thing is that it ought to depend upon the book.

In terms of fiction, I believe that most ebooks should be less than half of the price. I am losing the right to share the book with a friend, resell the book, and donate the book to charities. That is giving up far too much for something that I'll read once and never touch again. It is giving up far too much for entertainment.

Non-fiction is different. I am still losing those rights, but there is a high probability that I will reread the book or use the book for reference. I am still giving up a lot, but reusing the book increases its value. In cases like that what I'm willing to pay for an electronic version is in line with what I'm willing to pay for a print version.

The irony of the whole situation is a quote that I ran into on a Kindle or Kobo device (I forget which). It commented that reading is the cheapest form of entertainment, or something to that effect, and cited some notable author. With the prices that publishers are demanding and the lack of a secondary market, the quote is woefully incorrect.