@Alice1014 Instant Book is a booking setting the host can choose, which means a guest can just find a listing they like and book it, without first communicating with the host. If you didn't instant book, you would have had to send a booking request to the host, which the host can either accept or decline. So if all you did was find a listing and clicked on "Book now", that was an Instant Book.
The reason that hosts who use IB can get 3 non-penalty cancellations a year is that IB is riskier for the host- sometimes guests book who, after the host has exchanged a message with them, sends up red flags for the host, like the guest wants to bring more people than are allowed, or a pet, or communicates poorly or rudely, or doesn't reply to the message at all, or just sounds sketchy.
Hosts who require that guests send a booking request have the opportunity to chat with the guest before accepting or declining the booking, so they can get a sense of what the guest is like and ask questions to ensure it will be a good fit, as well as discuss any extra fees for extra guests or pets, so there's less chance for miscommunication or nasty surprises.
A good host wouldn't use wanting more money as an excuse to lie and say they're uncomfortable with the reservation, so in a sense, if that's what happened, you may have dodged a bullet with a bad host. In fact, a good host would never ask the guest for more money after they had booked, certainly not without explaining to the guest why. Occasionally, there is an Airbnb glitch and a guest will get charged some price much lower than what the host had it listed at, so in a case like that, a host may message the guest and explain what happened and apologize, saying they just can't rent for that amount, they'd practically be hosting for free. But it doesn't sound like that was the case here.
If it wasn't an Instant Book, the host will be penalized for cancelling, but some inexperienced hosts don't know that.
You should report this to Airbnb- it's very poor hosting form and unfair to guests.
