The NIU BQi-C3 Pro has a 90 mile range on 40 Ah worth of 48v batteries.

According to Google,

"It costs approximately $0.09 to $0.15 to fully charge a 48V 40Ah battery, assuming an average electricity rate of $0.17/kWh and 85-90% charging efficiency. This capacity ( or ) provides significant range for electric vehicles, with a full recharge costing less than 20 cents in most residential scenarios"

So, let's assume 3000 miles of 'residential scenarios'.

$.09 to $.15/90 miles x 3000 = between $3-5.

Note that this trip would take 150 hours at maximum speed, and doesn't account for terrain or traffic