How much equity would you put on the table and how much money would you want for it? Keep in mind that if you have a good pitch you can bring in $1,000,000 for no equity and if your game is successful it could bring in another $3,000,000 to $10,000,000.
Also, it requires that you have a (typically consumer) product that you can pre-sell. What if you are making a Saas that could turn into a profitable business but that cannot be launched on Kickstarter? It might still be a good investment opportunity so the other model could work.
I wonder what fair numbers would be. Hrm. Hard to say. A lot of 1-4 man small teams would do it on second thought. I think $100k for 10% is a pretty crap deal but creators would probably take that offer. Hard to know how Joe Public would respond. Definitely hard to predict after 5 years when people compile lists of games that even gave a break even return. Game companies and software startups don't exactly have a high success rate.
"0.000001% ownership per $10000 you invest"
"Sure, LOL, why not"
Now that we've established it could make sense, tweak the numbers to an equilibrium. Unless you've calculated that equilibrium, found it unworkable and skipped that step in the conversation and would like to enlighten us!