Thanks for including the version, but I don't recall there being a Sage 500 7.1, just 7.05 and 7.2. The reason it jumped to 7.2 is because the utility Sage used to track versions at that time rounded 7.05 up to 7.1, so maybe there is something that rounds 7.05 up to 7.1 that you're seeing. Either way, this is an old version. 7.05 was released around 2007 and ran on SQL Server 2000 and 2005, as well as correspondingly old Windows versions.

Since you aren't using a markup methodology, I would typically recommend using Global Price Group Change, but I don't believe it was added until 7.5/2013. If it is there, you will find it under Inventory Management / Activities / Utilities and it will allow you to select the price group type, which includes the different types of price models. You can restrict the data to a particular customer using criteria in Select Items but normally you can only restrict repricing to a customer if you have established pricing specific to that customer using contract pricing, customer price groups, etc.

If you really are on a version released before 2013, you might be limited to adjusting your contract or group pricing manually. You could also potentially contact your reseller or a consultant for programmatic help. I don't recall an automated repricing feature being available in versions prior to 2013, but it's been a while since I've had a client on a version that old so I'm not entirely sure what repricing features may have been included.