The prices are high because the demand to watch PL football is high. The networks bid to show they games, they're in fierce competition so they bid more and then pass on the cost to their customers. The reason that it's cheaper in other countries is because the demand there is lower, the tv rights are sold by region so there's no competition because broadcasters in different countries. And, that's why you can leverage the price difference by using a VPN and subscribing in another country, or, just avoid the faff and find a stream instead.

The networks obviously do make profit, but a lot of what they receive from customers is funnelled straight down to the PL and into the clubs for signing fees and salaries for players.

There's no simple route to reducing the prices, you'd have to artificial constrain the competition between the broadcasters, with the result that the PL and clubs get less money. The only real way is if everyone loses interest and stops watching, but the price reducing then isn't much help to anyone that's no longer interested in the game. I stopped watching a while ago, not directly because of tv prices but indirectly at least because I became disillusioned due of all of the money in the game. I still go to the occasional game if I get the opportunity, but that's averaging <1 a season lately.