How to read the number
Renting software is not automatically the wrong call. For a tool you pay $40 a month for, it is obviously right — the calculator will tell you so, and the build never pays for itself. The math turns the other way when a per-seat price meets a growing team, because you pay more every time you add a person, for software that does not change.
The seat count is the part people miss. A per-seat price is not a one-off; it multiplies every month that follows, and every hire. That is why the rental total keeps climbing with your team while a build is a one-time cost. The build is flat because a build finishes.
What the comparison tells you is how long your current spend takes to add up to the cost of owning the thing outright. Past that point it stops being about savings and starts being about control: nobody can raise your price, sunset your plan, or make you pay for a seat you are not using.