LTV is around 1000 sats? Typically how you'd structure these, assuming they're sybil resistant, is:

1. determine the lifetime value of the customer (how much you're expected to make from the average customer)
2. price the referral at half or more of that value
3. profit

For high LTV products, this works really well. For low LTV, it doesn't really have room for a good and profitable referral program.