Why does the price change after I click on "Request to book"?

[Magnus8]

When I'm looking at a listing for a particular time period, I see this:

And when I click on "Request to book" I see this:

If you do the math, the total adds up to 40967.63 THB. 

How come the price has increased by 3.5% here? I can't find any information on what's going on. For all I know, it could be some kind of currency exchange fee, but I'm not seeing any information about how they arrived at the new price.

Frankly, I find the pricing on AirBnb confusing and annoying. It's like the "good old days" on Agoda where you were shown a price without taxes and whatnot included - lame. First you're shown a nightly price, then the "actual" price for your dates, and then yet another price when clicking on "Request to book", and in some cases you'll find that the host mentions additional fees somewhere deep withing the listing description to be paid in cash on arrival... Any hotel booking site that had this pricing structure would be a joke.

[Greg171]

I have a 5-night reservation in Long Beach, CA in November. This is a flexible cancel policy reservation. After I made the reservation, I realized I need it only for 4 nights. The host is fine with the change in dates. I attempted to change the dates in AirBNB and the entire cost increased by $50, rather than being reduced by $130 or more - the price of 1 night.  Can anyone explain this to me, or is it an accounting error? There is no way to get information about such payment matters directly from AirBNB - as they have no customer service contact information easily obtainable.  Any information would be appreciated.  Thanks, Greg