Am i been taken for a ride by a freezer repair man?

Hi don’t know if there are any freezer experts out there?
My freezer in my store is not freezing properly, the bottom section is worse than the top section.
I have had a repair man out and he has said:
1. It need recharging at a cost of $250
2. It has a blocked pipe at the back which needs cleaning out at a cost of $350.
This seems a little expensive to me and i don’t really understand the whole pipe bit?
Can anyone tell me if this guy is taking me for a ride and if this quote is too high? $600 seems a lot for a bit of labor and some a recharge.