As for where the real gold flakes come from, google gold leaf, and goldbeating. Gold leaf is about 1/250,000ths of an inch thick. A packet of 100 sheet 3.5 inches square can be purchased for as low as $3.
How much does it actually weigh? Gold can be cut into very thin films or sheets and a lot of volume can be covered by a tiny amount, in which most of the space is air.
I have panned as well sir. What you find panning might look like these flakes they sell, but would be hudreds or thousands of time thicker. Most of these vials of "flakes" have been pounded out. Each one of the flakes you found Frank could probably be pounded flatter and make 10 or 50 of these made up "flakes". What are packaged in these bottles are too wide and thin to exist in nature, their thinness would cause them to break up and dissipate.
Know your sellers supply chain, as some Asian imports use copper alloy flakes, that appear like gold or aluminum alloys appear like silver due to thinness. Cost about 12 cents each small vial that sells for a few dollars. I have several small vials I filled by panning years ago alluvial gold flakes locally, and they are different in thickness.
Copied straight from eBay description... "This gold leaf flake is cut by a leafing company from scrap metals that contain only trace amounts of Real Gold. This gold flake is very beautiful and will fill up to 600 vials depending on the vial size. These beautiful gold leaf flakes are not designed to be melted down. I do not make any claim as to the percentage of actual gold contained in this flake. These Gold Flakes are sold to resellers & gift shops, placed in bags, vials and bottles for resale at a BIG PROFIT! It Looks Like 24 Karat."