Product groups are eligible for the Bid Simulator:
- Anytime after a product group is created in a Shopping campaign
- Once a budget cap has been reached for a product group
- Once the average cost-per-click (avg. CPC) is close to the maximum cost-per-click (max. CPC) bid
- When Product Listing Ads have been included in enough auctions or accrued enough impressions
The Bid Simulator collects and analyzes data from ad auctions on Google from the previous seven days, while considering information such as the quality of your ads, your competitors’ bids, and product data.
But keep it in mind that:
- The Bid Simulator is available when Shopping ads for a product group have been included in enough auctions or accrued enough impressions to generate a sufficient estimate of potential performance with a different bid amount. If you don’t see the Bid Simulator, you probably need to let your ads run for a little while longer or try to participate in more auctions by increasing your bids or providing higher quality product data.
- The Bid Simulator isn’t available for “excluded” product groups with no bid.
- The data displayed in the Bid Simulator for your “current” bid is a projection based on your traffic over the previous 7 days. If you recently changed your bid, you may notice notice a discrepancy between the “current” data reflected in the Bid Simulator and the actual data available in your account.
Read more here: https://support.google.com/adwords/answer/6239130?hl=en