National guide tables cannot capture every local premium or discount. Transport cost to remote areas, park rules, and seasonal tourism all move realised prices.
Use the guide as a midpoint, then apply your local knowledge. Low confidence rows especially need this second step.
When disputing a customer, show the quarter and spec rather than arguing the guide is "wrong" for their county - explain the limit of nationwide data.
Regional differences the guide may not model
Scotland vs south coast demand, transport, and site rules still need human judgement.