what other investment can you make 30 times your money?

Today I bought a couple of packs of Polaroid 600 instant film, each pack contains 10 exposures and they expired in 2002. Polaroid quit making this stuff about 3 years ago and since the price has been skyrocketing. I've bought and sold a few packs in the past and was pleasantly surprised at how much they go for. Last time they sold for $25, since then it looks like the price has risen. I bought them today for $1 per pack, that's a total of $2, I expect to sell them for $60 on ebay. That's $30 per pack. All for a few minutes of work, I was driving down the road, I noticed an estate sale, I stopped in, spent $2, listed them on ebay and now I wait for my $60. Not bad for a few minutes work.