I think you're getting such varied answers because it all really comes down to personal preference and spending habits.
For example:
For our first trip, we brought $300 in cash for random stuff. Well, we had never been to WDW before and were very frugal with our money. We bought beer some nights, but usually split one when we got back to the hotel. We weren't buying snacks that weren't on
DDP, because we were trying to "spend" those included in the plan to get the most bang for our buck. We each only got 1 or 2 souvies, and they were very well thought out. Most of our TS meals were buffets that already had gratuity included. With the $300 in cash that we brought, we brought about $150 of it back home with us. That trip, we were very budget conscious, as we were in our lives at that point.
Our 2nd trip - we spent willy nilly, and didn't keep tabs. I will tell you that about 4 or 5 days into our 10 day trip, DH and I did a loose tabulation of what we'd spent so far, and we joked that it was already over the $300 that we had brought on our first trip. We reigned it in after that and probably spent between $450-500 in spending money on the whole trip. But that trip, we were drinking alcoholic beverages at every meal, stopping in for a drink in Epcot's Mexico, or saying things like "yeah, go ahead and do the Pick a pearl for DD. It's not just a pearl, it's an experience!" We went to DTD and bought (severely overpriced) cigars to smoke as we walked, we bought DD a smoothie or something while we were having beers with our cigars... we just let loose. We weren't budget conscious at all, and we NEEDED that vacation as stress relief after some very demanding projects. We were glad to be in a relaxing place and were willing to spend the $ for creature comforts.