Hi, all. I am in the midst of a particularly soul-crushing job hunt. I just got word yesterday that the job I am most interested in won't be interviewing until the end of November. Having made it to the interview stage, I'm in a good position to get an offer of employment, but it's not guaranteed.

Because a lot of time went by between when I initially applied for and finally heard from Dream Job, I applied for other positions as well. One is interested in having me come for an in-person interview, but they do not pay travel expenses. This place is a three hour flight from where I live, meaning that I'd have to pay for airfare and a hotel. This trip would cost me at least $500. I'm pretty sure that I don't want the job, and I'd hate to waste my money and their time by going there. How to do I respond tactfully to the invitation to come in person? Should I cite expense as the reason? What should I say?