How do you figure that? I think I answered the question the same way every other person here did. The question was how long it took to break even on costs, not how long it took to develop. My time isn't a monetary cost.
Thank you. The arguments here that you need to calculate your time developing a side project at your market rate for clients or it "doesn't count" is ridiculous, and frankly kind of self-important.
A side project is something you choose to do, and saying you're still in the red because of your time, even though it cost you $4k to get off the ground and it's given you $40k back is ludicrous.
There are also ways you can mitigate the risk to some extent.
If possible build something your existing business needs. That way if it doesn't take off as a product you still have something that meets a need you have.
Launch the smallest thing that solves a problem your prospective customers have. The smallest thing they will be willing to pay for, then iterate from there.
Our product was something we needed in our service business (a small CMS that didn't insert unwanted markup) and took us about 4 weekends to get to launch in terms of the product, and about the same for the infrastructure around it (documentation, sales site and so on). It was tiny compared to where it is now, but enough people wanted it to make it worth continuing development.
A side project is something you choose to do, and saying you're still in the red because of your time, even though it cost you $4k to get off the ground and it's given you $40k back is ludicrous.