Here in the UK I think most ebook prices are reasonable. Some brand new ebooks are priced over £10 which in my mind is ridiculous and I won't pay that for an ebook no matter how good the book is supposed to be - I simply wait until the price drops which it inevitably does.
If everyone decided to boycott buying ebooks over certain prices then publishers would have to take note - hit them with your wallets I say!
One tip I have is to place all ebooks you want - no matter what the price - into your Amazon wishlist. Prices fluctuate all the time. Just yesterday I bought a book for just over £2 which was previously over £5. And the new Terry Brooks book was originally £16 has now come down to £9.99 although I'm waiting for the price to drop a little more before I purchase it.