A large part of compensation is probably not in base salary, that'd be asking for like a 50% compensation cut.

Even just base salary, if that's not something they'll stop paying the second you land a job somewhere else that could be completely reasonable. That'd be an extra 50% on top of whatever other job just to avoid direct competitors for the next year or so. I'd take that deal, and not just because an offer was contingent on it.

I was assuming the person meant what you take home. Not just base salary.

Correct. Edited comment to clarify.

I think there's some possibly quibbling around the edges around what exact would be included, or not. E.g. a rule that bonus / commissions don't have to be included, as long as that doesn't lead to < 75% of previous year's comp would still be ok with me.