Market Value

This might be a silly question and I know there is some nuance to it but I would be interested in people opinions/thoughts.

I know most people will use stockx as a base for valuing what the market is for a particular sneaker. Are you guys using the buyers view or the sellers view to determine what the market value is? For lower value pairs the difference is usually not a lot but for higher end pairs such as travis or rare sbs the different can often be $1k+ which makes it difficult to determine an actual market value.