The analogy in my head is the most excellent little bespoke bun shop I go to every week with my wife which is awesome. Compared to buns made for the masses in the supermarket.
Maybe there is a market for craft software as in craft beer :-)
Not that smaller customers are bad, but the ROI isn't as good. I've found that they're much more relaxed and easy to work with compared to working with other startups. The other startups I've worked with on deals often have shorter timelines and the person you're talking to is either a founder or early employee and has way more stake in this transaction that a manager at a larger company does.
In my experience, the customer that brings in the least money also makes up for most of the work. It's a larger percentage of their budget. For a Fortune 500, your fees could well be a rounding error. These small guys are also the ones who would go out and post bad reviews, demand the most features, demand the most uptime and the fastest response times.
Free users also have lower expectations. Low-paying users might not be worth the hassle. If you sell candy by the hundreds of kilograms it's better to give free samples than to sell little bags.
The point being how big of a workflow advantage someone would have from a paid account and their business goals based on that.
Adobe suite is a great example - student pricing, normal pricing, teacher pricing etc etc.