Jordan is right, that comma wants to be a <
that is
If(
ToDays([Hotel Check-Out Date]-[Hotel Check-In Date])<=7,ToDays([Hotel Check-Out Date]-[Hotel Check-In Date])*25,
If(
ToDays([Hotel Check-Out Date]-[Hotel Check-In Date])> 7 and Today()<[Hotel Check-In Date],7*25,
If(
ToDays([Hotel Check-Out Date]-[Hotel Check-In Date])< 7 and Today()<[Hotel Check-In Date]),7)))
That solves for syntax but I think you still have a problem in that that condition actually won't resolve since it's a subset of your first condition. This will have been the case in your Excel version, too. If I'm understanding your use case correctly, it looks like you want to reorder your conditions.