Bull Crap! I don't taxi much, but I have on occassion when on vacation, and I don't think I've ever had a taxi ride under $15.
Let's see, I took a cab from my house to SF once, a total of about 12 miles and the ride cost me about $90 (plus I had to pay for the bridge fare).
I recently took a cab in the LA area from the Airport to a person's house only a couple miles away, and it was about $50 dollars. I was charged about $7 right off the top just for the fact that the ride started at the airport.
I took another cab in Seattle this past year, from our hotel near the airport to the cruise terminal and the fee was about $80 at least.
The closest I've come to getting charged what you said was in Las Vegas that was only a mile or two and it was $15. After finding out how short of drive it was, my wife and I walked back instead of catching the cab.
Don't know where the heck your riding cabs for $10 (with the tip included), but in my little cab'ing experience, I've never found one. I think they'd charge you that much for driving to the end of the block. Most cabs I've seen charge you a couple bucks before leaving the curb and to start the meter.