Kicky:
Well, call her up and say that if that's the condition that she'll go with you, you'll accept her money. You just really want to go, and you'd like her to go with you. Tell her you thought she was joking about paying for it.
I, personally, would be thinking "this guy's SERIOUS" if he offered to take me somewhere costing that much money so early on... unless he was made of money, of course, and threw it everywhere... maybe the cost is a statement to her of your intent?
However, I still stand by my feelings that she should have said more clearly, "I'd love to go with you but am uncomfortable with you paying for my ticket at this stage. I'll go if I can pay for it."
If she won't go with you, I will.

(And I'll even let you pay for the ticket, heh heh)...I love Sting (and the Police, of course!)... I saw them both here in Vancouver, about 25 years apart!