This is a great question. To be completely transparent, we are considering a flat fee because of the reason you stated.
We originally chose a percent fee because it was an industry standard model that many in the carbon offset space expect. However, we're learning that industry standard here does not mean it's the best possible option.
The big reason why a % fee is good is because for small donations (e.g. 25% of someone's footprint) it makes more sense to scale it. A $4 transaction cost on a $2 impact to the project is crazy.
The tricky thing about our cost structure is that currently we do not have enough revenue to cover our overhead expenses, so even if we're ignoring the per transaction cost we need to find a way to cover our overhead (e.g. a place for us to live so we can hack on this all day)
what about letting your users get a % of all the money from collected from users they invite?
They could either receive those as Stripe payouts, or further reinvest their earnings into curing global warming
i.e. cure global warming MLM style
This could also open up some nice customer acquisition strategies benefit from asymmetric motivation: teenagers/kids bunch of teenagers (who would spend hours persuading their rich parents /grandparents to donate $50/mo, such that in return the teenager earns $5/mo). This may be able to help mitigate the problem that older people are less likely to believe in the severity of global warming than younger people - in the same way that your grandma bought your magazine in 5th grade (so that you could win a prize, not because she actually cared about the magazine) as part of those gamified magazine fundraisers in elementary school
would love to schedule a call with you to see if there is any pro-bono help I could do. I've thought about a couple creative solutions w.r.t to donation psychology, and have actually pitched ideas similar to Wren before at events. I do full stack web dev and have a couple of ideas for visualizations/UX that may help increase donation/referral behavior
Combining both of your models, maybe take a percentage but capped to 20% of the customer's footprint? The hero who wants to offset 200% of their footprint would still just pay 20% of their footprint, i.e., only 10% of their donation.
We originally chose a percent fee because it was an industry standard model that many in the carbon offset space expect. However, we're learning that industry standard here does not mean it's the best possible option.
The big reason why a % fee is good is because for small donations (e.g. 25% of someone's footprint) it makes more sense to scale it. A $4 transaction cost on a $2 impact to the project is crazy.
The tricky thing about our cost structure is that currently we do not have enough revenue to cover our overhead expenses, so even if we're ignoring the per transaction cost we need to find a way to cover our overhead (e.g. a place for us to live so we can hack on this all day)