If you haven't explicitly set unique pricing for an event, the price of the products are set to whatever they are set to at the supplier level.  This is designed to help with global edits to pricing.  However, there may be an occasion when the prices in your event are the same as at the supplier level, but you need to "lock" them in before making changes at the supplier level.  This is a common scenario when you have price changes in a new year, but the existing events at the end of the current year need to remain in place.   

If you use the Event Product Price Import to update an event's price, your prices are different than the supplier level pricing and are already "locked". There no need to lock an event's pricing in this case.

Locking Pricing

To lock one or more events' prices:

1. At the top of the Event Grid, click on "Lock Event Pricing".
2. A Picklist appears allowing you to select the events for which you want to lock your pricing.  Use the Search Criteria area to either search by event name or by event date.
3. Click Apply Criteria.  The resulting events appear on the left side of the Picklist.
4. Move them over to the right side by hitting >> or double clicking on the event(s).
5. Click Apply Selection.
6. After processing, the pricing will be locked down.

There is a security setting that determines whether a member of a security role can perform the "Lock Event Pricing" feature. It is set to enabled by default for store administrators, and set to disabled for all other roles.

Locked Pricing Indicator

When a product's price has been locked, an icon appears in that product's row within the Products grid of the event:

The column labeled "ELP" stands for "Event Level Pricing" and is the indicator that the product's pricing has been separated from the product at the supplier level.  Any update to a price at the supplier level will not impact the product's price of the event you're in.