Bought in Store
The average size of a trading card gaming deck is anywhere from 30 to 60 cards depending on the game, and prices seem to vary from game to game. A 60-card Pokemon deck in September 2009 hits most stores for about $30, while the 11-card booster packs sell for 3.99. A 40-card Yu-gi-oh deck sells for $19.99 and the nine-card booster packs are about $3.99. A two-player starter pack of Harry Potter, which contains 82 cards, sells for $19.99 while the eight-card booster packs are $2.99. A 60-card Magic the Gathering deck sells for $19.95 while the 15-card booster packs are $4.49.
Bought Online
If you prefer to go online and do your shopping, you'll usually be looking at the same prices as in brick and mortar stores unless you decide to buy in bulk. Different merchants may offer discounts, usually around 20 cents per item of purchase on purchases that involve 10 or more items.
Personalized Decks
If you are more into the competitive side of trading card games, you might commission an individual to make a deck for you. Sometimes tournament officials will offer to make you a deck for around $45 to $60 plus the cost of the cards. The benefit to having a deck made like this is that the official has had more experience with the cards and knows the positives and negatives of each strategy. However, if the strategy has been around for a while then there are likely decks out there made just to beat the strategy.
Identification
It's always important to know a little about what you are buying, especially if you are not buying sealed packs and you intend to trade cards. There are those out there who make fake cards and try to sell them. Each properly printed card has a set stamp somewhere on each card. Some cards contain an identification number that can usually be found in the bottom right corner of the card. If a card should have one of these stamps but does not, the card is most likely a fake.
Misconceptions
One major misconception about trading card decks is that there's instant cash in them. A lot of misinformed collectors will stockpile booster packs with the assumption that in a few years those unopened packs will fetch a high market price. The only times this will happen is if the company that prints the cards closes while the game is still popular, if the company discontinues printing a specific set or if there was an unbroken or extremely powerful card in a set.