If you don't want a pay cut, don't apply for the job, unless it really means a lot to you to do it. Simples.
I'm speaking as someone who made a lifestyle choice when I was very young. I've never earned anything like the amount stated in that job advert (I'm 50 now), but I've thoroughly enjoyed every aspect of what I do. Had I made a choice based on income I would probably be in a very different place now, and not half so happy. Every business decision I've ever made has been based on how much enjoyment I'll get out of doing something, not how much money it'll make me.
I'm sure there are plenty of other hard-working folk out there with a similar mindset who'd love that job, regardless of the wage.