Expensive is a relative term, but if the parking fills up, then it’s probably not market pricing. When market pricing is used, there will generally be a few open spots. Because if day after day there is more demand for something than there is supply, suppliers will increase the cost and continue to do so until the market reaches equilibrium.
But city parking is very expensive and still often fills up, and the free parking at suburban Walmarts usually has plenty of open spots.