I sold my first online product today, a spreadsheet with a list of biotech startups and VCs, for $350. I found this customer through a google ads campaign that cost ~$200, so it was a mildly profitable sale. I also cold emailed a bunch of people and that led to some sales conversations but no sales. I think the price was too high.
Unfortunately the customer isn't a type of customer I'm looking to pursue: they are a procurements company that has clients across all industries. They don't seem to have much of a focus on biotech. I frankly don't even know why they bought the list. So this is probably not a step on the path to sustainable revenue.