My most expensive item found at a SA in my whole life was a Strawberry shortcake plush doll from the 80's in box that I sold for $80, I paid $2. This doll was not worth that much right away though, when I got home it was going for about $10 on ebay, I had to hold onto it for a whole year and constantly check up on it before I got the $80 for it so there was some work to it. A close second is a lot of Sailor Moon dolls I got that I paid 99 cents each for, I sold the dolls for $60 then I sold 1 single doll from the lot for about $25.
I did get a Neo Geo Pocket color last year for about $5 in box and near perfect condition with 2 games and an accessory pack. Haven't sold it yet mainly because someone like this is so hard to find in my area. I don't think I have seen one anywhere in my area outside of this one time.
I also got a Nomad for $6 at another thrift, again a rare item for my area. Definitely the only one I have ever seen out in the wild.
This stuff doesn't come often though for me, these finds are very few and far between. Though I have to say I hardly ever go thrifting. I am sure if I was stopping in once every week I would find more stuff, but my trips are limited to once every few months or so. The thrifts are just too far apart and not close enough to my house for me to make it a regular occurance. If i lived closer to the thrifts then I would go more often.