I've just made a new listing and enabled smart pricing. Pretty quickly, I received a booking enquiry. This was for 8 nights with the various smart prices for each night (£521).
However, after a couple of questions when the guest made a booking request, the price dropped to my minimum rate x 8, and didn't represent the nightly smart prices.
*** Note: I'm not currently offering weekly/long term discounts and I haven't made a special offer.
The nature of smart pricing is that is constantly fluctuates although that said, I would have thought that if the guest had already made an enquiry at the rate of £521 then so long as the same guest requested to confirm the booking within 24 hours the price should have remained the same £521- perhaps contact Airbnb directly to query this.
@Chris121 - something similar happened to me over the weekend. I got ahold of Airbnb via Twitter and they had a case manager get ahold of me to correct it.