The value of a domain extension depends on how much it is branded to the end-customer -- resulting in the name being memorable (i.e. people not typing in the ccTLD and/or .com). For example, no one in here knows anything about .asia but they all have .co.in (yes, even more than .in -- though it is changing slowly) branded in their minds as it has been used by companies like Yahoo in India.
Pro is an extension which has never put any money into branding the extension to the end users -- and there is a lot of corruption at registry level. We tried and nearly succeeded to get realestate.pro -- however, there was fixing at the registry level.
Good that we didn't get it cos I am yet to see any good aftermarket sale. =) I hope you didn't pay anything above the registry fee for these domains.