> an expensive interview process where the candidate has to be onsite

I'm sorry, but if I'm doing the hiring, the person who isn't willing to come on site to do an interview will be one of the first people off the list to hire (I mean, unless it is a remote job, and the person is nowhere near the employer, obvious exceptions would apply).

In-person interviewing can be extremely valuable. Will it filter out every bad candidate? No, some people excel at faking it. However it can be a big help in finding a good candidate.