@Louise543
Smart pricing fluctuates because it's "smart." Depending on how many people are searching your area or clicking on dates, the price can increase or decrease (stopping at your min and max price set.) But this does not happen every minute. You will usually see prices fluctuate every day or so, if that. So, thinking about your guests ... it's like you see an outfit on sale over the weekend but when you go back to buy it on Monday, the sale is over. Sorry, you should have bought it when you saw it.
But you do have 100% complete control over your prices, so if you want to give these guests the lower price, then go for it. You can send them a special offer with whatever price you'd like.
Also, keep in mind that when the guests "go back to book" they might not have realized or factored in the Airbnb service fee (which can be quite high) or taxes.