I once read that the fundamental runner strategy could be written down as "Draw cards, get breakers, get money, run." There are exceptions, Noisemill decks being the most common deviant, but most runners follow this general pattern.
Drug Dealer helps one of these steps at the expense of another. Drug Dealer draws you cards, but costs you money. And it does so at the base rate of equivalency; 1 = 1 = 1 card drawn. So why would this be a good thing?
Well, simply put, it's easier to turn cards into money than it is to turn money into cards. Take the simplest example, Sure Gamble. If you have a Gamble in hand, then the next time you would spend a click for a credit you can instead spend a click for a gain of 4. This means that the mere act of drawing a Sure Gamble is essentially worth 3. So if Drug Dealer gives you a Sure Gamble, he's paid off for that turn and the next two.
But, you need money to run, and drawing cards doesn't help that. (Unless you're playing Faust, of course.) If you're spending all your Sure Gambles and Daily Casts just keeping up with your dealer, then you're never going to have the money you need to actually install breakers and get in when you need to.
Meaning that if Data Dealer is your draw solution, you need to have a lot more economy in your deck, for two reasons. The first is consistency in your draws. If you've got 9 econ cards in a 45 card deck, you will see some money every fifth card on average...but you might have a dry spell of 7 or 8 non-econ cards in a row, and with Drug Dealer keeping you broke the corp has ample time to score out. Going up to 12 or more econ cards helps keep dry spells short.
The other reason is that a lot of economy in Netrunner is impermanent. Event-based econ is single use, and Daily Casts, Armitage Codebusting, and Liberated Account all run out eventually. If these are your economy, then there are only so many credits you can efficiently gain, and many of those are going to get burned to Drug Dealer. So you either need to run a lot more of it, or fall back on stable, long-term investments like Magnum Opus, Kati Jones, Desperado, Underworld Contact, or Data Folding.
A few closing thoughts:
- Drug Dealer is a connection, and if you have enough other connections you can make use of Calling in Favors or double down on the draw with Off-Campus Apartment.
- It's not unique: you can potentially be having a three /three card swing each round.
- At only 1 influence, it's easy to move into other factions, although Shapers already have plenty of options.
- If you are running broke (with Faust, for example) then you can cheat the dealers out of their money.
- Drug Dealer CAN cause you to lose the game if you overdraw your deck. If you're afraid of this, you should plan to use Aesop's Pawnshop or Chop Bot 3000 to remove them before this becomes a problem.