There's a concept around a lot of preliminary engagements between two entities called "skin in the game." The idea is that when something is completely free the other party will take advantage of it without any real serious intent to follow through on anything.
Mostly this seems a reaction to the homework-type assignments where candidates are expected to spend a lot of time on some interview assignment with very little real cost to the company--which raises the possibility that it's effectively a cattle call.
I could run 50 candidates through a $200 problem for 10K. That's still a pretty large mismatch between "amount of work done by the candidate" and "amount of work done by the interviewer," and is cost-of-doing-business money for recruiting for a lot of companies currently.
Compare that to the cost of me flying people out (which is still done in this approach), or even the cost of spending an hour of mine or someone good on my team's time on the phone with them.
I guess it's just down to the difference between trying to hire fresh-out-of-college (or still in) free-time-to-spare junior devs and experienced people. That's actually a topic I should write a blog about somewhere myself, one day - I pushed pretty hard at my current company for moving towards a different process for industry candidates, and are extremely pleased with some of the people it's helped us hire.
I do agree that if people are flying around, that represents a fairly significant investment in any case. But in Silicon Valley, that often isn't true.
It's hopefully a case of coming up with processes that don't encourage people to waste others' time. But that also assumes some reasonable balance of power in the process.
Even after that, the "experience candidate phone call to see if they're worth flying in" part is definitely the one where I have the hardest time, being not in the Bay Area. I was lucky to find some great local people, where the cost was lower, because that's an expensive one to have to get good at fast. You lose a lot of nuance over the phone, though some other people in the company have been having very good luck with homework in this case - but as a candidate-choice option, where they could still go the traditional route if they wanted.
It's easier than it seems.
Just put a HackerRank test with a single question. "Print the numbers from 1 to 10 [inclusive, one number per line]".
20-30% of candidates won't attempt the test. 20-30% will be unable to give a decent solution.
If you're running 50 people through this, you're doing it wrong (unless you have 20+ positions).
I don't understand why you think improving your employment situation wouldn't be hard work.
I'd much rather travel and meet you in person and do stuff there, but if you don't have the budget for it, we could figure other stuff out (shared docs, skype, whatever, I've done a few of these on both ends with some luck).
"Since the candidate is getting paid" seems like far weaker motivation than "since the candidate wants the job you're offering," which is what's going to determine my level of effort.
The "not a real problem" thing is key, though. I've tried testing out a few different "this is one of our real problem" things but there's almost always more hidden business rules or assumptions in there than you think.