It's pretty much a "Must" to have multiple battery packs.... Motors are not as important.... Theoretically you could have 1 all weekend. And yeah theoretically you could have 1 battery all weekend, but we all know to be competitive you need more....Especially in on-road.
So a motor $40 to $110 (If we go by retail)
Batteries (5-10 of them) $500 to $1200.
You ask the dimise of electric racing!!! I certainly do not want to have to update my batts every month.