If this is true, then those of us who bought level-2 chargers paid an awful lot of money for a relay.
Yes, there is charger circuitry in the car. But there is also active charger circuitry in the box between the wall plug and the J1772.
yes, you are correct, the active circuitry in the EVSE is not simple or trivial, but it only does those basic functions. Ground fault detection for safety, relay control (the logic on when to close or open the relay based on safety and handshaking with the car), and generation of the pilot signal (an electronics signal generator, a low frequency signal with parameters that tell the charger the max current the charger in the car can draw), there is also some filtering and surge protection.
Some EVSE, like my ChargePoint 32A unit has a microcomputer and circuitry for power monitoring and WiFi reporting.
Also, there are a number of protection and filtering components, such as varistors (often blue or red thick discs) and chokes (sometimes heavy wire wound over ferrites).
Reliable high voltage (240V AC) relays for relatively high currents are not inexpensive.
But, you nailed it on cost. That is the reasoning most folks give, when you see posts like, "
I made a L2 charge cord for $30 in parts from Home Depot".
OTOH, reliable, code compliant, UL rated, etc., L2 "high voltage", "high current", electrical gear is not inexpensive, nor is the relatively thick stranded copper wire that must survive many cycles of use and coiling and weather. Same for enclosures like Clipper Creek that are designed for outdoor use, weather proof and at least water resistant if not water proof, over wide ranges of ambient temperatures.
Here's another way to look at some of the active electronics in the EVSE. The EVSE must sense a ground fault condition, preferably before closing the relay to energize the cord, and afterwards while charging. That decision cannot be made at the charger in the car, because before the determination must be made before the cord is used, before it is plugged into the car.
A lot of that active circuitry is dedicated to not powering the cord between the electronics box and the J1772 connector if something is wrong.