Lots of people asked how many people are backed PA. In this forum i found the group "PA Early Backers" with the description "Forum members that backed Planetary Annihilation via Kickstarter or PayPal". There are currently 39608 users (03. June 2013, 10:04 pm UTC+2). Source: 1.) Link: memberlist.php?mode=viewprofile&u=1773902 2.) Use the "Groups" menu to open the "PA Early Backers" site.
But the real question is, can all of those people get into the same game? Maybe we can ask China if we can borrow their 54.9 petaflop supercomputer.
Going by pure kickstarter numbers off the top of my head as im on my phone, around 7000 had access to Alpha alone from their, then you have people like me who upgraded. So what do we think around 15,000 for Alpha status?
I think around 8000-9000 from Kickstartert at 90+ dollars? Then there might be a few that paid with PayPal and then some that are going to buy at Steam directly when Alpha starts... Your 15k sounds okay liamdawe. But depends on how many actually bought it with Paypal(we don't know this... in my country credit cards are not that common and we use other payment which is not available at Kickstarter so a few including me might have bought with Paypal) and how many are going to buy it with Steam(90 dollars is a lot of money and Steam people usually are whining "why should I buy this they should pay me to test their game").
Just tallied-up the KickStarter page. There's about 8,100 backers who are in the alpha. A further 12,000 backers who have beta access. And finally, 23,720 more people who backed the game, but only for the retail version. KickStarter says there's 44,162 backers. Some of those haven't finalised their pledges and connected their Uber accounts. Then there's Pay-Pal to factor in.
It's all unverifiable statistics, but I'd guess there's at least double the backer count than were in the kickstarter. Because kickstarter is big, but it's not as if it has universal coverage.