For variant regular price, Inventory Planner uses item retail price ('retail' price list). Price (current) is taken from default sale price list configured in Settings/Configuration/Price Lists.
Note that we also use real price from sales order when computing revenue and profit.
Moving average cost is used for item cost price to compute cost-related metrics in reports. In purchase orders, Inventory Planner uses supplier price list (if configured in settings)
or default buy price list set in Settings/Configuration/Price Lists.