The player featured on the card – Cards featuring legendary or star players tend to retain the most value over time. Players like Babe Ruth, Mickey Mantle, Jackie Robinson and more modern stars like Mike Trout, Bryce Harper, etc. will almost always have cards in demand. Even role players or never-were prospects can have valuable rookie cards.

The year and brand of issue – Older vintage cards from the early 20th century through the late 1980s are usually more valuable, as those early printing runs were much smaller. Also, some brands like Topps, Bowman and Leaf have historically been more coveted by collectors.

Condition of the card – A card’s state of preservation is absolutely critical to its worth. Near mint/mint condition cards in the highest available grades from services like PSA or BGS can be exponentially more valuable than worn/damaged cards of the same player/issue. Raw, ungraded cards are tougher to value.

Rarity – For vintage cards especially, rare variations like error cards, unique serial numbers, scarce parallels, and 1/1 patches or autographs command the highest prices. Even a common card can gain value if few surviving examples are known.

Current player performance – For modern issues (mainly 1990s-present) involving active players, their ongoing career success very much impacts card prices. A superstar in his prime will carry premiums over post-retirement versions of the same player. Injuries, controversies, and declines can have negative effects as well.

General collectibles market – Wax box and unopened pack prices tend to rise during bull markets. But individual cards also track general economic conditions and collectors’ risk tolerance over the long run. Recessions can temporarily depress values across the board.

With all that context in mind, here are some specific observations about the baseball card market in 2018:

Vintage cards remain strong – Pristine examples of iconic 1920s-1980s players continue setting record prices at auction. A Mint-graded 1952 Topps Mickey Mantle just sold for over $2 million, underscoring steady institutional interest. Commons from the golden era still appeal to new collectors.

1990s boom hits 25-year mark – This hugely productive period for the hobby is reaching “vintage” status itself. Ken Griffey Jr. and other stars are peaking in demand from nostalgic 90s kids who grew up with them. Prices reflect increased appreciation of the designs and players from that era.

Prospecting pays off eventually – While few true “rookie cards” command big bucks right away nowadays due to larger print runs, cards of future stars purchased cheaply provide opportunities. Players who debut and then have breakout seasons see past issues spike in value from initially cautious collectors. Risk and patience are keys here though.

Modern parallels prosper – Inserts, autographs, memorabilia cards, and limited parallel versions of current superstars like Mike Trout are steady performers. As rookie classes get larger, rarer variations offer collectors opportunities to profit by finding the hidden gems earlier.

Unopened wax stays pricey – Sealed 1986-1987 Topps boxes continue setting new records above $20,000-$30,000 as safe, tangible investments. Other complete vintage sets do well too when graded gem mint. Powerful brands remain crowdpleasers for prestigious mainstays of collections.

Online auction sales robust – Between eBay, Heritage Auctions, and more specialized third party graders/sellers like PWCC, auction prices tend to accurately reflect current collector tastes and market values. Increased global reach and competition inflates final figures.

Digital cards arrive – New blockchain-based platforms create collectible virtual replicas that can be bought/sold/traded. It remains to be seen if they gain mainstream adoption, but could open the hobby to younger demographics more comfortable in digital spaces. Values fluctuate wildly in these early experimental markets though.

While not achieving the frenzied heights of the early 1990s bubble, the baseball card market remains vibrant and multi-tiered. Smart collectors can still find plenty of affordable entry points at commons boxes or lesser-known stars’ issues, while high-end vintage cardboard poised to set new benchmarks. Condition, research, and long-term appreciation continue paying dividends for dedicated fans in this timeless field of collecting.