How to buy plane tickets for job interviews?

I am currently on the academic job market, and scheduling on-campus interviews with institutions that might want to hire me.

Suppose I am invited to an on-campus interview at the University of X, and must travel there by air. They handle travel on a reimbursement basis: I buy the plane ticket, and then they reimburse me.

However, the interview is a few weeks away. Since the job market sometimes moves fast, there is a chance that by the time of the scheduled interview, I may have already accepted another offer (say from the University of Y). Of course I should then decline the interview at X, but I would have already bought the plane ticket.

How should I plan for this contingency?

1. 
   

   I could buy a refundable ticket to X. However, these are normally several times the price of a non-refundable ticket, and if I do end up traveling to X, they might balk at reimbursing me for such an expensive fare.

   
   


2. 
   

   I could buy a non-refundable ticket to X. If I end up not going there, I could ask X to reimburse me for the cost of the ticket (or at least the "change fee" charged by the airline to let me use the ticket's value for a future flight). However, I suspect they will be reluctant to reimburse me for a trip I'm not making, and might refuse to do so altogether, in which case I am out-of-pocket.

   
   
   


3. 
   

   I could wait until the last minute to buy a non-refundable ticket for X. But it may still be expensive for them (or may exceed their limits), and the most convenient flights may be sold out.

   
   


4. 
   

   I could contact University of X and ask them for guidance. I'm a bit hesitant to do this, as I am afraid that if I bring up the possibility that I might accept another position, they might think I am not seriously interested in theirs.

   
   

Is there a standard way to handle this situation?

This is in the United States, if it matters.