So, it sounds like the screen part has changed, but obviously not $500 changed. So what else might have changed?
The screen part might have to be bought in larger minimum quantities. That could imply hedging some of the risk by raising cost - ie, they have this screen, but they have to buy 10,000 of them, not 500 at a time. You could either hope to sell tons, or just raise the price a bit to cover some risk.
Also: BOM cost to final cost varies, but 5:1 isn’t a bad rule of thumb for a product that makes money, so a $20 screen price-hike at supplier translates to another $100 you pay.
If they’ve not only changed screen, but changed manufacture partner - potentially not just for the straightforward things like the electronics, but the aluminium (which is fairly premium and they would have high tolerances on), that could impact pricing. It’s unclear if that’s happened.
Let’s also include inflation: $799 in 2011 dollars is $915 in 2019 dollars, so at least $100 of that pricehike is ignorable.
So: we have maybe $100 of inflation, perhaps $100-$200 of screen costs (because of a $20-$40 bom hike from screen alone). That’s before you consider anything like manufacture changes, higher cost of doing business. This doesn’t get me to $1299 in one fell swoop, but it does creep there slowly.
And: they’re a business, selling a product, and if they can sell the number of them at the price they ask - ie, the market will bear it - then there’s not necessarily a reason to make them any cheaper. Not all companies want to shift as many units of a thing as they feasibly can; sometimes, they want to sell the amount a 40-person company can deal with. Just because Korg or Yamaha could make the same thing cheaper doesn’t mean everybody should. Whether or not you think that’s “greed” is up to you.