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What is the advantage of using ReviseInventoryStatus instead of ReviseFixedPriceItem?
When just the price and quantity of an item has to be updated, ReviseInventoryStatus is recommended because it is a light-weight call. ReviseInventoryStatus call completes quicker compared to ReviseFixedPriceItem call and consumes less resources on the eBay servers.
In addition, ReviseInventoryStatus call can be used to change the price and quantity of multiple listings (upto 4), whereas ReviseFixedPriceItem can be used just for a single item.