Time is the biggest thing to consider. In a crowded metro area, drive times to and from can easily turn a "30-minute" mini-session into a one-hour there, one-hour back deal that takes, actually, three full hours! ACK!!!!!!!!
One thing I have noticed low-end mini-session shooters doing is scheduling multiple mini-sessions at one good outdoor location. Combining even two short sessions at one location, back-to-back, can cut the effects of drive times down quite a bit, and lessens logistical hassles too. Two, 30-minute sessions, back-to-back at $100 each is $200/hr. Of course, the final part is to be able to pose, shoot, and process the images VERY quickly. And by very quickly, I mean 30-40 seconds per image. The way the modern, higher-volume portrait and event pros do it. Not slaving over images, but creating images that are done right, in-camera.Finding and or creating/modifying the light, at the scene, is what the best shooters do. You simply can not take shots that need "heroic" or even level 8 rescue processing and make any profit if youi have to spend 10 minuites per image at the computer.
You cannot "perfect" each and every image down to the last fine detail at these kind of prices. You will need to start with fundamentally good lighting and excellent posing. The way old-time professionals did it.
If you're going to shoot this low-end stuff, you simply can not spend a lot of time perfecting sub-par or "needs-work-to-make-it-work" images. This is the way shot-on-film used to work: you lighted the images right, from the start. It's a different mind-set.
$100, 25 minutes shooting maximum, five poses, one CD. ONE person, one location, one clothes change, each additional person $35. That pricing is actually almost double what I see around here from these mini-session new pro's.