Most? I can't think of a gig beyond maybe a couple of folks in a coworking space where I wouldn't be laughed out of the room with "just make it 150% of salary and we'll figure out the real number whenever". Virtually every company I've ever worked with budget the actual number, because they know how much the overhead cost is. There's a huge difference between "a number I use when asked 'ballpark how much a new hire is gonna run us'" and "what is the amount of money I'm asking the CEO to allocate me in next years budget".
Depends on the kind of work you do and the competition. A former employer was really desperate for pretty journeyman-level Django Dev help a few years ago and for some reason it was just super tight. Ended up paying more like 350% after looking a few weeks. We obviously weren't going to hire someone at that rate for a 6 month contract but for short term help? Sure.
Well, sure...there's always a one-off where you have to throw out the rulebook on salary. But any HR team worthy of the name can still compute the actual overhead on that base pretty much to the dollar.
