Going back a few years (2011-12) a straight-up Coke in Pacha was €6-7. Which - in that season at least - worked out marginally cheaper than their btl of water. And you got more fluid for your buck if you requested no ice.
I don't for one minute condone or enjoy spending €10 - €15 on a single drink, but there are other factors to consider. Yes, it's a rip off. But if they did decrease prices they'd have to hold considerably more stock on site. Is there space for this? Would they run out? Does the islands infrastructure accommodate this: delivery lorries, warehouses etc.
Bar waiting times would increase - ppl will simply buy more drinks as their money will be going further. They'd have to employ, train & pay more bar staff, laymen, supervisors, which in itself is costly.
Is there even space behind the bars for more bar staff - let alone extra stock?
As a few above posters have alluded to - their business model has found balance.
The water price though - that's what irks me, and what I consider to be a separate issue from the price of alcoholic drinks.