Since any large tech co knows what Facebook offers look like, if you have an unusually good offer they might not believe you without proof and they certainly won't be able to expand the pay band without approval from someone. The easiest way to make that case is showing the actual offer.
This is one of those things where: if you never get them to tell you "no that's too much" you probably aren't asking for enough
Just ask yourself. from their side are you going to require proof for what they say? Will they comply and show you profiles of people they consider before you? Probably no. The game is rigged. Act accordingly.
