What should I do if Carvana's offer seems low?

Get at least one or two competing offers from other buyers before deciding. CarMax, regional dealers, and broker services will all generate different numbers for the same car. If Carvana is at the low end of the range, you now know that and can decline with confidence. If it turns out to be competitive, you can accept knowing you did your homework. Never accept the first number without knowing what a second or third buyer would have offered. The time this takes is usually less than an hour and the upside can be significant.