IMHO comments like this are much more valuable with some numbers.

The linked figure[0] and associated paper report that efficiency peaks for EVs at around 20mph and then the cost per mile increases roughly linearly, by about 25 watt-hours when the speed increases by 10mph.

Please excuse the archaic units.

[0] https://www.researchgate.net/figure/ehicle-energy-economy-at...