If you currently make $100k, go through 4 rounds of interviews, and all the prep for each round, then you get an offer of $50k, you've just wasted alot of your time. (Very valuable time). Sure you might be one heck of a negotiator and convince them all the way past your current salary, but if you are that skilled in negotiations, you should already be making way more than $100k. Even if they do negotiate, you've already established that they don't value this position, or they do value it, but they look at thier own employees as a cost center to attack to increase thier margins ,opposed to an asset that increases thier overall revenue. Either way, it's not a company or a position you should want.

When I first meet with the recruiter, I tell them what it would take for me to consider a move, this probably weeds out 75%+ of positions, and I'm okay with that, because I value my time, and I don't want to waste it interviewing at cheapskate companies.