Garage Sale to Antique Mall

I just came back from a local antique mall for a new TV report that will be on our show soon. What surprised was the amount of "garage sale" inventory that was for sale at high prices. I was shocked to see old boxes of Tide Laundry Detergent, filled and never opened, selling for $35 and what makes them valuable is that this "original box" came from the 1940s. Now, I can't guarantee you that it is indeed from the 1940s. But I can tell you that there were old record albums, old sets of china, old soft drink bottles and lots of old "throwaways" with price tags that surprised the heck out of me.

It got me thinking that a lot of garage sale items that you can pick up for "real cheap" can quickly be turned. And here's why I say that:

The box of Tide came from someone who walked into the antique mall, and said they wanted to sell the Tide "fast" and settled for only $5 (five dollars). The operator of the antiques booth at this mall checked some online listings for old boxes of Tide, determined that it was worth $50 based on previous eBay sales, and put a $35 price tag on it.

Well, would you pay $35 for it? I wouldn't. But if I found an old box of Tide that I could turn around and sell double what it cost me in a garage sale I'd consider that to be a pretty good return.

I found out that Tide was original developed and sold in 1943 and this might have been an original box.

I have heard of people making a living at this. Does anyone here have experience making money off of garage/yard sales?