I think your forgetting that parks will have to be running on potentially 1/3 or 1/4 capacity, will have to invest in PPE and extra sanitisation measures and also carry out work to make changes throughout the park such as adaptation to queuelines/groundwork so that new social distancing floor signs can be placed down.It might be worth remembering, though; if UK parks are allowed to open in June/July, they have the entirety of the summer holidays to make money, and the summer is a huge period for theme parks. Surely they wouldn't want to miss out on summer income?
I think it’s great your optimistic but if you are only allowing 1/4 of daily capacity in, you are only getting a 1/4 of the return you otherwise would have, and for some parks the cost of running is going to outweigh the cost of staying shut for the rest of the season.
This is still assuming parks will even get to open up this summer. Theatre tours and shows are inevitably cancelled until at least September. I’m just struggling to comprehend what the practicality and safety of parks opening their doors really is. And then even if they can, with reduced return due to extra investment in PPE, sanitisation and lower visitor numbers, is it even economically viable.