Baseball cards have a history of being sought-after by collectors because of their material and sentimental value, especially graded baseball cards. Nearly the same to those you find now commercially available started out in the 1860’s. It’s because of their long history and wide usage in the US, Canada and even Japan that they are a favorite among collectors. There are some rare baseball cards which are worth millions of dollars, so it’s no wonder people are doing their best to turn their cards into valuable assets.
About Graded Cards
At first, cards were produced independently or by tobacco companies. It wasn’t until early last century that mass production of cards began, with it being halted or greatly diminished during the two world wars or during a decrease in nationwide baseball interest. But they’ve sprung up over and over again, and the game itself became more and more popular over the years.
Grading has been introduced as a way to determine value and price for the card which would soon start to become valuable trading assets. Given that some rare cards could be worth thousands of dollars, authorities in the field started providing 
services in terms of grading baseball cards. This meant taking the card, analyzing it properly for wear and tear, making sure of its authenticity and determining whether anything had been done to alter its condition after it was packaged.
Grades are given from 1 to 10, where 1 is the lowest quality and price and 9 or 10 being considered mint and gem mint condition. Baseball cards which are graded 10 are very rare, as the grading authority will need to check things like surface, corners, centering or edges. Customers then receive their encapsulated cards back with the label bearing an ID, serial number and the assigned grade.
First and foremost, people choose them for their value. Many serious collectors of valuable cards won’t mess around too much with cards that have not been graded, except if they’re old and haven’t gotten around to a grading company yet. There are several grading authorities in the US including PSA, Beckett and SGC.
Second of all, it helps establish whether the card is unaltered and original. People often wonder whether an ungraded card holds any value and the answer is usually yes, but without it, you can never be sure of what you’re about to invest and as a seller you may not realize the price you should.
It’s easier to sell graded material if you’re trying to find out where to sell baseball cards.
As of this writing there are over a half million graded sports cards on eBay.