Also you are making a purchase of a product as is. No promises were ever made. Plans can change.

You are not making an "investment" as you put it.

In fact the price of the game may very well go up when it gets to full release. And it is well worth the cost that it is at now.

Do not spend your money thinking you are putting that in some kitty for future development. They have enough money, they don't need your "investment" but are happy to sell you their fine product.