They might be part of the location description, though it might not
really be necessary.
> 2) When are taxes applied? If I buy a sword for no more than
> x, is that before or after taxes are applied?
They simply become part of the displayed product prices in the market
report. You needn't really know how much of the price is tax and how
much is original cost. You decide to buy or not on the aggregate.
> 3) What's to stop Warlord Jimmy from set region tax 500?
Ever heard of the Laffer curve ?