[runako]

The questions & considerations you ask are all valid, and are generally included in the buyer's evaluation process. Every point is extremely subjective and not precisely knowable. That's part of the fun of business!

But you are obviously correct that there are no risk-free transactions.

> It might even be cheaper (incorporating risk) to build a $500 / month business than to verify the purchase of one.

Here I want to point out that I know a number of talented people who want to launch a business, but for whatever reason cannot get to the "launched, accepting money" phase of their projects. These people have no problem improving an existing business, but have trouble going from 0 to 1. (I believe this population is as much as 100x the population of people who have successfully launched & gotten revenue in an app.) For these people, it might be entirely worth knowingly overpaying for a working SaaS because it gets them past the launch phase. Putting it bluntly, would they rather spend $10k on an app with revenue that you can grow or another $50k of nights and weekends over the year with no launch to show for it?

Edit: I also forgot that there's the entire category of buyers who just want to keep the app as-is and either integrate it into a bigger suite, use its traffic for lead gen, or otherwise leverage it for some other purpose. If the buyer considers the purchase as part of its marketing budget, $5k is not very much at all. (Plus the bar is low as most marketing spend is wasted, see the adage.)