Gundam Front in Odaiba, Shot-G?

Hello,

We will be in Tokyo in April, and were looking at going to Gundam Front during our stay in Odaiba.
I was looking around the Japanese site (despite not knowing Japanese) when I noticed this thing called Shot-G? Several in our group are now very interested in this! It is possible to buy them the day of visit, yes?
And there seems to be three prices, 1500 yen, 2000 yen and 2700 yen. I think the most expensive is if you buy it the day of? So what is the 1500 yen option?

Sorry I have so many questions, we are just starting the planning process and are so very excited :)

Thank you very much!

Here they say (for adults) the entrance ticket to Gundam Front cost 1,000 (advance booking) and 1,200 (same-day ticket), and in addition for Shot-G itself, 2,000 yen (advance booking) and 2,700 yen (same-day ticket). One Shot-G ticket allows max. 3 adults getting photographed together, but you get only one set of 2D and 3D photos.

http://gundamfront-tokyo.com/jp/ticket/

Oh, I see the 1,500 yen now... that's for an extra copy of the photos.

They seem to sell the tickets in advance too, so no guarantee that they will be available, but same-day tickets are sold.