I'd also like to know that! I have some ideas, from less shady to more:
- Payment for order flow
- Interest on sweep accounts
- Upsell to more profitable products (first party ads)
- Payment for order flow, but structure your orders so the spread is really attractive to market makers (unfortunately you might be doing this unintentionally)
- Third party ads
- Sell your customers' data
There's also the possibility of not doing any of these, losing money in the name of customer acquisition, then selling to someone who will monetize it better.
I find it a bit rude to ask a company their exact business plan, even on Launch HN, but maybe I could ask - are there any of these monetization strategies you disdain and would specifically rule out? And if you do have one or more of these in mind, is the $1 really important, or is that a marketing trick where people wouldn't trust you if it was free?