Back in the 1990s, there was a massive onslaught of variant covers from multiple different publishers. From Marvel to DC to Image, everyone had a foil variant, a variant color scheme, or an exclusive cover that you could only get by buying a game, toy, or sending away a coupon on a cereal box.
The release of Spider-Man #1 in the early 1990s was really the culmination of so many things that were wrong with the comics industry. Multiple covers, multiple colors, foil, poly-bagged… This issue had it all. All the flash and bang that comes from creating a show, packed into a comic book event. This was the first time in a while that there had been a new Spider-Man series. Also, the addition of Todd McFarlane as the artist to the series was a big event.
Around the same time, there were issues with foil and chromium covers, black covers, white covers, sketch variants, and many other types of things coming from Image comics. Now many of these issues are worth only a few cents or a couple of dollars at most.
So, comic books can be a speculative market, meaning that shiny is not always valuable. And some of the most mundane things, regular covers, filler issues, and lame sidekicks, can turn into something amazing and valuable beyond reason.
Comics got very popular through the years. They have developed to Hollywood movies, TV series, PC and online games. Companies recognized the potential of comics and started to integrate them into their products to attract customers. One good example is internet casinos like MansionCasino.com that did it perfectly.
Investors have tried to buy and sell comics for many years in hopes of finding a formula. The winners, though, tend to be the comic book publishers. The secondary market is nothing but speculation.
The truth of comic collecting is really in collecting what you love. Read a bunch of stuff, find some characters that are interesting, that you relate to, or that you just find cool. Then, go out and buy all their stuff. You are bound to hit on a good one once in a while, and it may just be that you picked up the next Walking Dead #1 or first appearance of Spider-Gwen instead of one of the million variant covers of Secret Wars.