I've been selling a couple of WordPress plugins since 2013, mostly piggy-backing on other popular services that were experiencing crazy growth and taking care of their WordPress integration for them (unofficially, some already had one that sucked). Yearly (subscription) revenue is at about $500K USD now. It has been growing by less than 10% for the last few years as I haven't been that interested in growing it - I wa…
I'm developing Advanced Forms (https://wordpress.org/plugins/advanced-forms/), not nearly as popular as your plugins but makes for a nice side income.
If you have the time I'd love to hear how you've been promoting and growing your plugins over the years. I find that aspect of the business challenging and have mostly been relying on outside help.