I had the most humiliating experience of my life interviewing with AirBnb couple of years ago. https://news.ycombinator.com/item?id=5300104
1. Don't pay for anything out-of-pocket for a fly-in interview without solid assurances you won't be screwed (What assurances do I have your accounting people won't give me the indefinite run-around?) or disbursement delays forever (When can I count on being repaid?). Expense reimbursements normally requires receipts, prior approval (specific person in HR or hiring mgr) and talking to accounting to submit the right f…
For example, why does Google sometimes take close to a year to make a decision on a candidate? Because they can afford to, with a pipeline of thousands of qualified candidates enough of whom will be OK playing along with Google's timeline in exchange for the significant CV boost, higher salary, prestige, experience, etc. The same applies to university applications - a lot of people will spend fortunes in time and money to try and get into Harvard, Stanford or MIT because the upside of having these schools on the CV is so high. Both prestigious jobs and universities (whether or not they should) do open doors, allow you to raise more funding and faster, to get higher positions all things being equal, to get your CV read in a pile of 200...
So it comes down to valuing each position's Net Present Value (NPV) and the probability of it being a success, and deciding whether this is the most attractive use of your time and money. Let's say AirBNB has an NPV of (an additional) $3 million over the next 10 years thanks to the network and career boost, and you have a 5% change of getting it, the value of taking the interview is still $150k. Assuming you weigh negatives 9x as high as positives (can't remember where I read about this cognitive bias), if the interview has a total cost (including opportunity cost) of under $16k it is worth doing. Of course, at 5% chance of success per position, it's probably worth applying to more than just AirBNB.