Offer your product to startups for free to convert them to loyal customers over the long term.
Intrinio ($10,000/mo) gained several new customers this way. They launched a program offering six months of free data to startups. Of the 70 startups that signed up, many stuck around after the program ended, leading to plenty of revenue with little added effort. If you want to create your own startup program, try promoting it in the Indie Hackers Deals group and in other communities where your audience hangs out.