I have created custom prices, price sets & service plans and while provisioning the instance it shows the configured price according to the service plan. However if we want to change the service plan for that specific instance, it is not showing the configured prices. I have not set any region code for price sets and plans, also the currency is set to USD for prices & subtenant.
NOTE: This is for VMware cloud resource provider.
Are you sure that the price set is attached to that plan you are selecting? Also, are you doing a reconfigure at the instance level, or the direct VM level?