"Best Price Guarantee" sounds like a hotel benefit. It is an OTA mechanism. The OTAs use it to enforce parity informally — when a guest finds a lower price elsewhere, the OTA refunds the difference (eating the margin) and uses the case as evidence to pressure the hotel into compliance. The trap is that the hotel often does not know the parity break exists until the OTA bills them for it.
How the trap works
A guest books your hotel on Booking.com at €180. Two weeks later they find the same room on a smaller OTA at €165. They claim Booking.com's BPG. Booking.com refunds €15, then opens a parity ticket with you — asking you to either (a) match the €165 rate on Booking.com going forward, (b) explain how the lower rate appeared on the other OTA, or (c) reimburse Booking.com for the BPG payout.
Most properties find out about this when the KAM's email lands. By then the leak has been monetized against you, and you are negotiating from a defensive position.
Where the lower rate usually came from
How to defend
First: do not assume the BPG claim is valid. Ask for evidence (screenshot, URL, timestamp). 30-40% of claims are stale (the lower rate has since changed) or are comparing different room types or different cancellation policies. Second: if the claim is valid, identify the source channel and shut it down — this is more important than the immediate refund. Third: keep a parity-break log so you can spot patterns. A wholesaler leaking three times in 6 weeks is a contract conversation, not a one-off complaint.
The bigger picture
BPG exists because OTAs have a structural interest in keeping their displayed rates the lowest. The mechanism is designed to externalize the enforcement cost onto the hotel. Every hour you spend defending BPG claims is an hour you are doing OTA compliance work for free. A property with a clean rate-plan architecture and a tight wholesaler set has 5-10× fewer claims than one without.