I think you should absolutely ask to go see them. Reason: you learn way more about people in person than you do on a phone/video call. In fact, if I was in the startup and I was planning on spending roughly 10X that amount every month on an engineer, I would want to spend that money to vet the candidate thoroughly.

Also, 1.2K+ ?! It costs me $800 to fly from NYC to Stockholm. Are you in Hawaii or something?