Rough price for 14-50R installation in Maryland?

We have an existing 30 amp 220V outlet in our garage for a wall heater installed by the previous owner. We had an electrician come out and give us an estimate - he said that the existing outlet is too low for the cable length on a typical charger (it is near the floor) so he needs to install a junction box, and he can add a new 14-50R outlet (for the 32 A charger) plus restore the existing outlet to the junction box. His formal quote:

Furnish and install 14-50R tapped off of existing wiring. Includes installing junction box and re-installing existing receptacle. $660 total.

This is about double the expected cost - considering they is no need to install the 220V wiring/breaker. Is this quote unreasonable?