Like any established market, collecting original comic art has become easy to start. The value of individual pages has fluctuated but the high end of the market has exploded into tens and hundreds of thousands of dollars a page. While new comic art is always being generated (at least until all artists switch to digital production), there is a finite amount of original art by each artist which provides a limited supply. The market for new comic pages continues to be robust but there is no guarantee on future values.
There are a variety of factors involved in prices you may pay:
Scarcity - Some pages are lost forever, some artists do not sell their original art, some have donated their art to museums, some artists only had a small body of work, etc. Like any collectible, the rare items tend to cost more.
Artist - Not all artists are equally popular. For newer artists you may be able to get the pages cheaper directly from them and if they go on to greater heights their original art value gets more expensive to acquire. Conversely, new artists on "hot" books typically price art at a premium and if they don't go on to become legendary the art may actually go down in value over the long term. Another factor is how many artists are involved. Are you buying a pencil page, pencils + inks, or inks over blue lines. In many cases it is the pencil artist that is demanding the premium, but sometimes they are more highly collectible when paired with certain inkers.
Type of Page - Covers generally command the highest prices but splash pages (single image on entire page) and double page spreads (single image over two connecting pages) can also be expensive. A guide to the various types of original art can be found here.
Character - People generally want the main character featured in a nice panel/splash. Like most things in comics today, super-heroes tend to rule and pages with large images of the heroes in costume command higher prices. Most comic stories will have pages that involve the hero out of costume or won’t have the main hero at all, those pages are typically less expensive.
Content - Is this an important moment in the history of comics? Is this an important moment for the character? A first appearance of an important hero or villain? A number one issue? Did this comic go on to become a popular TV show/movie?
Condition - How nice or how beat up is this page? Many of the corrections are applied by pasting corrected artwork directly to the page. Those corrections can dislodge and be lost. As noted above, these were not designed to last forever, the materials were not selected as such and the storage conditions were often not ideal. Some remediation attempts can also cause more damage in the long term. We advise against any such home attempts with consultation with an archival expert. Such information is more widely available now. For more expensive purchases, you will want to closely examine the condition, but in the end, if you like the page it is unique, so you should get it regardless of condition if you love it, just make sure you pay a price that reflects the condition.
We would generally advise that you buy the art that personally interests you for a price you are comfortable paying. People do make money in this market (as with any) but collecting as an investment is beyond the scope of this small introduction. Remember the value of any collectible is how much anyone will actually pay for it.
The most important thing is to have a good time and find what you like. Happy hunting.
At a minimum keep art out of direct sunlight and intense artificial light and away from heat and humidity. You can store art in portfolios or frame & display it.
Portfolios - Itoya makes nice storage solutions in a variety of sizes that are acid free and archival safe. These can be purchased at art & craft stores like Michael's or Aaron Brothers or on-line from places like Dick Blick Art Supplies.