Not exactly sure of the context here, but most rays at fish shops...especially Castexi varients are wild caught specimens. Which mean they have been caught, put in a container, put in a distributors tank, starved, bagged, shipped, put in a distributors tank, starved, bagged, shipped, put in the shops tank for display where they "try" to get them to eat. Bagged, put in the buyers tank...then the buyer has to get em eating and healthy.
This a lot of stress for a ray. That being said, I would MUCH rather buy an established, healthy "second hand" fish any day. Are prices cheaper when buying from individuals...usually, because they do not have the overhead. Are they healthier? only if the individual has good husbandry skills.