I've never charged per page before as pages can take a few minutes to add, but getting to grips with the theme and any custom changes are where the most time is spent.

Have you got a suitable theme? Or will you have to find one?

Ultimately it comes down to how much to charge per hour, and then estimate how long it will take you.

Will depend a lot on the client and how picky they are with the design and how much custom work they want done. 72 pages doesn't mean anything because it can take minutes or hours to implement a page. Also, 30 days isn't very long at all. What if you have a question and it takes 1-2 days to get an answer back from the client? What if you hit a roadblock and have to outsource some coding? What if the hosting gets really slow for a few days? Lots of things to slow you down. If you don't deliver on time you will lose a lot of credibility or worse, get sued.

I've created a few large sites, but have actually shifted my focus to smaller 5 pages websites for this reason. Much easier to price, less obstacles, and I can get them done faster. Plus I usually get bored working on the same site for weeks on end.

As for the website, I'd imagine it would take up your full-time for the month, and would have little time for another project. I'd charge what a month of your time is worth.