As a general rule, an electrician will charge you 2 to 3 times more to instal an EVSE than they will to install a 14-40 outlet.
The ubiquitous 14-50 is old tech, it is super common for RVs and pricing for such an outlet has been set for years.
EVSEs are new fangled. The market allows for more margin, so many, if not most electricians will use that excuse to charge you a lot more.
So, if 10kw (40a) is enough for your needs, buy your EVSE with the 14-50 plug and save yourself some money. A further benefit is portability and expandability in the future using splitter switches.