Swiss and Edelweiss do not have any flights where the goods are not exempt from VAT/Excise/Tax. (LX does have domestic flights but there are no on board sales). Not surprising that they only have one price. My experience with both is that their on board prices are less than non-exempt high street prices here. Where, outside London, would you pay £4 in the UK for a small beer?
Have a look at your receipt next time you fly U2. Do you see the VAT number? No you don't, because it ain't there. So no VAT going to UK/Swiss governments (depending if it's U2 or DZ). Excise and duty dealt with as an accounting entry, (they can show export based on sales receipts).
Ryanair doesn't fly to CH. However I imagine they and Wizzair apply this same rip-off on their non-EU flights It really isn't better just because they all do it. I've not flown either so cannot comment further on these two.
A price what the passenger is willing to pay is still a rip-off where the passenger has no choice and, in fact, is prohibited by law from buying (alcohol) elsewhere.
Yes, I know, just don't buy it. That still doesn't make their non-EU pricing fair and reasonable. It is a rip-off.