First of all like any crowdfunding buying early give the opportunity to make the project happen. It's also an ability to get the premium currency at a discounted price. Also there are a lot of advantages purchasing during the sale. There are rewards like very limited cards. The genesis card or the satoshi card for example. The card that we distributed at limited supply like the FDCARD already have a lot of value. We saw an ask price of 110 XCP on counterparty decentralised exchange. Most interesting purchasing BitCrystals during the sale open the door to premium and partner store. Those store are limited to people who reach certain ranks. This give the ability for people to be resellers. They might have access to cards that we are not selling anywhere else. This way they can open their own shops.
There are more info about the rewards here http://www.bitcrystals.com
The art of a good game design is to give unlimited fun for people who don't purchase and incentive and advantages to people who pay.
So our job is to find the right balance in order to keep free players and to maximise revenue from paying players.
Getting paid to build something or baking a project is the base of crowdfunding. Like there are millions on Kickstarter. The main difference between Kickstarter and this project is the fact people are buying part of the game economy. The blockchain nature of Bitcrystals means when you purchase something in the game it retains it's value just like physical objects. You have full ownerhsip of it. If you want to trade it, share it or whatever it's up to you. You can even build other games or products that are using those assets. There is a win-win situation because if the game gets popular the demand for the game asset will be important so people in the community are empowered to promote the game.