For some high-level positions, it gets negotiated up-front. You're leaving some other company, taking a risk, and there's a good chance you might not be right for the new company.

But if you're less high-level but rare and desirable, well, some situations, like moving cross-country, might make it a bit appropriate.

> I was under the assumption that companies offered severance pay as a means to save face.. and this is not part of the offer negotiation.

Quite the opposite- this is how exec compensation works. It seems less common in startup land but I've dealt with it before

Everything is negotiable. You can negotiate a private office with a ocean view if you're valuable enough. This won't work for rank and file employees obviously.

anything is for sale and on the table, you just have to ask/demand it. Doesn't mean you're going to get it though.