So photoshop is 2x the price in the UK (where I live) due to cost of living, but my colleagues in the states earn 1.5x my salary also due to cost of living? Does not compute.

It's not the cost of living nor the cost of technical support as one of the responses discussed, but the fact that EU law places so many additional constraints on businesses that the cost of doing business there is vastly higher than doing business in the US; accordingly, US companies make up for the difference by charging EU customers more for their products.

The EU does certainly not place restrains on vendors which DOUBLE their costs. Is Windows twice as expensive? Are apps on any appstore twice as expensive?

This is just Adobe trying to rake more cash in. They are betting that companies are not going to switch from Adobe products to something else because a licence is twice as expensive. So far, it seems to have worked.

Except in countries like Australia your support is frequently based in West Coast US and India / Philippines yet your still charged an uplift.

If Support location mattered, you would have hawaii being charged differently from the other 49 states for every bit of software. As it is I have at least 2 hours of cross over with US business hours. If I bought the US software and had to call in during US hours, THAT would be understandable. No local free call number... that is understandable. But NOT just not selling it.

In the modern environment, if your entire transaction is via the website and the support rep is in india, why does it matter if I am buying from the US or Australia through your US store?

Surely the only cost is currency exchange, which I have to cover anyway on my Credit Card.

What is new (at least to me) is that Adobe keeps the price difference for their subscription plan. You can install whatever language you want - but you have to pay the local price.