Booking a trip and the service fee changes

[Sam109]

I'm looking at booking a trip to Cap-d'Ail in the south of France.  When I search Airbnb without signing in (or through an incognito tab), the Service fee is shown as £53.

When I sign in and come back to the same apartment, same dates, same number of travellers, the Service fee has shot up to £67:

What gives?  Why am I being penalised £14 for already having an Airbnb account?

[Clare0]

@Sam109 the service fee also includes VAT, if you are subject to that tax.  The only way Airbnb knows to include VAT is when you are logged in. 

[Sam109]

That makes sense - thanks Clare.  I also realised after I'd posted that it might be related to exchange rates between France and the UK.