The skill I built for my product turned out to be sellable on its own

For the last 4 months I’ve been building Xedge — helping people find the right AI tool stack for their specific goal.
This week, needing to cover some short-term costs, I realized something: I’ve been doing this exact service for free in DMs for months. Someone asks what they’re building, I figure out their AI stack, I reply with the breakdown.
That’s a sellable skill completely separate from the product itself.
So I’m testing it directly — listing “AI stack research and setup” as a freelance service while XEdge keeps compounding in the background.
The lesson here: sometimes the tool you build to solve a problem at scale has a manual, sellable version hiding inside it. Don’t assume the only output of months of building is the product itself — the expertise you gained along the way often has its own market.
Anyone else found unexpected income inside a skill they built for something else entirely?