Possibly, but it's usually not the price of the ebook itself that they are complaining about. It's the fact that the paper version is cheaper. If someone charged £10 for a particular ebook and £15 for the paper one, then there would rarely be much complaint. If they charged £10 for the ebook and £5 for the paper one, then people are up in arms.

And the argument is alway that it's cheaper to make the ebook than the paper one, and that it's therefore wrong to charge more for the ebook. The point is that this is the wrong way to think about it. As a buyer working out how much you're prepared to pay for something, the cost of manufacture should be pretty much irrelevant. If the ebook is worth £5 more to you than the paper one, then buy the ebook. If it isn't, then buy the paper one instead.