This page is a work in progress and incomplete. If you have any suggestions please pass them on. Some of the cover images on this website link to pages that display images of original Star Trek art, thus my interest in the topic.
I'm strictly an amateur when it comes to Star Trek comics original art. I've been buying Star Trek comics artwork for several years. I've never sold any art. My knowledge is mostly from observation of what I've found on the net and in local comic shops.
I've seen several types of original art for sale, from pencilled art all the way through the printing process to printer plates. I'm sure this isn't a complete list of what might be available.
A color guide is created on a photocopy of the original inked comic art. The copy can be reduced to 8.5x11 like yours or it might be full size, about 12x18. I think reduced size is more common. One of the comic's artists or an artist hired to color the inked artwork will use color pencils, felt-tip pens, watercolors or any combination of the above to create a color guide which the printer will use for printing the finished comic. Today, most comics are colored digitally, so hand-colored guides are less common.
Value is a more difficult question to answer. Star Trek comic art is generally less expensive than artwork from superhero comics. Star Trek comic art on eBay is generally less expensive than art sold by comic art dealers.
Opening bids on pencilled and inked 12x18 original art on comic art board for Star Trek comics interior pages range from $10 to $300. Most opening bids fall in the range $20 to $50 and final prices fall in the range $20 to $75. Interior original art pages are the most common item for sale. Some items with high prices are Buy-It-Now items. It's not unusual to see high-priced items on eBay keep reappearing for a long time.
Opening bids on cover art range from $300 to $7000+. The highest opening bids are for the painted cover art from Gold Key Star Trek comics which are typically acrylic paint on heavy art board. I've bid on a few covers, but prices for cover art increase beyond my budget pretty quickly.
Opening bids for color guides range from $10 to $25. Final prices usually range from $25 to $30.
When a comic is finished, the artists may get to keep their original artwork. Some artists sell through dealers, on eBay, or from their own websites. An artist may photocopy their original art, hand-color the photocopies, and sell them. The result is similar to color guides. Opening bids on this type of artwork range from $10 to $20. Final prices are in the same range.
In all cases, the final price of an item may be skewed by someone collecting artwork by a specific artist, from a specific comic, or because the artwork features a favorite character. Pages or covers with large images of familiar Star Trek characters tend to get bid up. Cover art is almost always more expensive than interior art.