They are free for the first year or two of owning an EV (most EV's come with a free charging subscription for 1 to 2 years at various charging networks, with Electrify America chargers being the most popular and the ones at Wal-Mart's). If it wasn't for that free plan, it'd cost about $15 to drive about 200 miles (about 13 miles per $1) (assuming driving 80 mph in my EV).
Of course, the first 250 or so miles are charged at home. If I didn't have solar at home, it would have cost about $11. In my last power statement my utility charged me 15.7871ยข/kWh (after subtracting flat monthly charges). So count it as needing 70kWh to charge up (assuming a 5% loss when converting AC to DC during the charging process). In my case, with solar the charging is practically free (my solar provides 80% of the power consumed in our all-electric home, including charging the EV). It's almost entirely free for local driving because the EV doesn't have to be charged every day if we drive it just 40 or 50 miles (in that situation I can wait up to 4 days comfortably for a good sunny day before I charge it). But for charging up before a trip, I always charge it completely the day before no matter the weather (so let's say 80% of my trip charging from home is free).
Looks like all of the charging stations near us are at $0.37, at least for Tesla style chargers.
A Wal-Mart down the road has three types of chargers. The slow one is 50kW, and is priced at $0.19. They also have 150kW and 350kW chargers, both at $0.37.
Finding a 350kW charging station would make me drive to the Wal-Mart if I needed a charge.
As you said, most EVs come with some free charging, and discount cards are available at the website.
Looks like you have a sane situation, between the EV and solar at home.