Answer:
Hay una pequeña diferencia aunque los dos sean verbos copulativos.
There is a slight difference even though they are both copulative verbs.
Step-by-step explanation:
Normalmente usamos ser para hablar sobre cualidades permanentes de una persona. En este caso "es muy caro" significaría que siempre tiene un precio muy alto.
Normally we use ser to talk about permanent qualities of a person. In this case "is very expensive" would mean that it always has a very high price.
Usamos estar para hablar de estados temporales. "Esta más barato" significaría que igual dentro de dos meses sube el precio.
We use estar to talk about temporary states. "It's cheaper" would mean that in two months' time the price might go up.