I KNOW they don't profit and never said they did. But they do have to price their "books" 20%+ higher in because they are selling a licence (which incurs tax) and not a book which doesn't.
It's nothing to do with whether they're selling a license or a "copy". All sales of goods/services/licenses are/were subject to VAT unless they are specifically exempt - physical books are exempt,"electronically supplied publications" are not. If you sell digital "copies" of books (and have more than £70k - or whatever it is now - annual turnover) then you have to pay VAT on sales.
I get it - you want the government to use VAT as a lever to force sellers to drop restrictive licenses - but VAT legislation is a can of worms at the best of times so that would be like using a supernova to crack a nut. It's also something that probably couldn't have been done under EU law (whereas that 2-year-old directive allowed simply cutting the VAT) which still applies until next year (and even then, fantasy Brexit rhetoric aside, it would be complex and expensive to diverge from EU law just for teh lulz - especially ones that could affect digital commerce). That's also assuming we have a surprise general election and an even more surprising change in fortune for the Pirate Party - because none of the main parties have shown any interest in "fixing" copyright and licensing. Anyway, those license restrictions stand on on flimsy ground w.r.t. doctrine of first sale, "contracts of adhesion" and the sale of goods act anyway - if the government were so inclined they could end them with the stroke of a pen.
Meanwhile booksellers could also drop the price of eBooks vs. paper on the grounds that they don't have to be printed, bound, shipped around the country/world, carry a discount for retailers, not to mention all that mess about having to guesstimate how many copies to print, suffer lost sales if you under-estimate, have to pulp unsold copies if you over-estimate... I'm not holding my breath.