110 PSI should only equate to a very small temperature drop from the ambient temperature.
I have a feeling that either his pressure check was done without the A/C being turned on, or that his pressure gauge is malfunctioning (or your temperature gauge is bad, but you'd be able to tell if it wasn't hardly cold at all).
The high pressure port (where this measurement is taken) lies between the compressor and the oriface tube... Once the refrigerant passes through the oriface tube, it is 'sprayed' into the evaporator, kind of like a garden hose sprayer attachment. This decreases the temperature of the refrigerant, which makes the evaporator very cold.
Then the blower motor blows air through this cold evaporator, thus making the air cold out of the vents.
I would strongly recommend having another mechanic look at it, for a second opinion. I'll try to dig up some diagrams for you, and get back to you.