Translation:They pay ten million for the hotel.
The infinitive is in American English too.
"A couple wins the lottery. They decide to buy a hotel. They pay ten million for the hotel."
My understanding is that the course uses the infinitive as the suggested translation because Swedish doesn't have a separate present tense, and it's important to remember that the Swedish words you're using are not specifying present tense—you need to be careful what you say so people know you're talking about the present, not a story that happened some other time or a habit you practice regularly.