I wonder about this also as more customer are going to hard floors in their homes.
I get a lot of calls for 1 or 2 rooms as that is all they have now, so with a higher minimum it make more customers shop a little more.
I just did a job this week for a property manager. Turned out to be 1 room that was aprox. 8x10. I stilled charged $120 even I was there for only 20 minutes. Take into consideration the time it takes you to have the truck prepared with the appropriate tools and supplies for each job, a man and a truck driving to the job site, setting up the tm or bringing in the portable, doing the job and packing everything up and going on to the next job, then cleaning up at the end of the day. If you had to pay someone to do this for you, what would you charge? Never mind the other overhead you have to pay such as fuel, insurance, phone bills, advertising, rent, etc. If your competitors are doing jobs for less, let them. They will be losing money, you won't. When you get these small jobs, take your time and do the best you can. People appreciate the service. Don't think that you are expensive. When someone calls you for a 1 room job, tell them it's only $120. Don't say this is your minimum charge.