I've set the precision parameter to 9, entered the price 123,123456789, but after saving the price changes to 123,123400000. What's the problem?
The extension changes only price display, not the price itself. Magento database tables limit prices to 4 decimals — it simply ignores everything else. So if you really want to have more that 4 decimals, you'll have to edit some Magento tables. But we really don't recommend doing that.