What things ask in exchange, spoken plural — price in money, tokens, or effort, counted honestly.
Old French coster (to cost), from Latin constare (to stand together, be fixed, cost), from com- (together) + stare (to stand); what a thing stands at in exchange, counted honestly whether in money, tokens, or effort.
What things ask for in exchange, counted honestly whichever currency it is paid in — money, tokens, or plain effort.