@Joseph1235 I wouldn't try to "hash this out with the host". There's really nothing to hash out, unless you are willing to meet them in the middle and they are okay with that. Hosts have to honor the pricing that was there when a guest books or cancel the reservation themselves. They are asking you to cancel because hosts receive heavy penalties from Airbnb for canceling reservations. One of which is that their calendar will be blocked for the dates they cancel, so they woudn't be able to rent it to anyone else, at least not through Airbnb.
Yes, they likely forgot to update their calendar that far ahead. But that's their issue, not the guest's responsibility. If you decline the new price, they will be forced to either honor the original price, or cancel themselves. But I would ask myself if I really wanted to stay at a place where the host was behaving unprofessionally. Personally, if I were in your position, I would contact Airbnb, explain the situation, and ask to have the reservarion cancelled with full refund to you and look for another listing. For a big event weekend, likely other places will likely be much more expensive, but it's far enough in the future that hopefully you can find something you can afford. As you said, the price seemed too good to be true, so you were probably planning on having to spend more anyway, untilyou spotted this place.
And you wouldn't want to take a chance on them agreeing to the original price, only to cancel closer to the dates because they got a better offer through other channels, leaving you scrambling for a place when most are already booked or super expensive.