You are the sixth (seventh?) economy of the world, you are expected to pay more. Did you expect Austria to contribute more than the UK? The EU has some associated costs, which need to be paid, and there is budget for investing in depressed areas (many in the UK).

But don't worry, you will get 30 different trade deals which do not cost any penny in supervising or enforcing, because that just happens automagically: you sign in the bottom of a paper, and all written rules are respected, enforced, supervised and updated. Isn't that sweet?