Those who have taken apart the electrical connections that connect a 220 v wall outlet to an EV find there is very little inside them. Other than some relatively simple safety features, they are basically a 220 v extension cord with the right connectors on both ends.
Why so expensive? At this point, its a small volume market and they can charge too much.
Source: What does an EVSE actually _do_? | Chevy Bolt EV Forum