Google’s product structured data help documentation has been updated to include a section for price drop appearance, which supports displaying price drop rich results. This will only count for English users in the US, as well as both desktop and mobile search.
According to Google, “to be eligible for the price drop appearance, add an Offer to your Product structured data. The price must be a specific price, not a range (for example, it can’t be $50.99 to $99.99).”
Source – Search Engine Land