Of course you're throwing money away. Blizzard charges you for the right to play a game that you already bought (there should be a law against that, it's ridiculous), even though other online games give you that option for free. If you have a choice between, say, WoW and TF2, then playing WoW costs you an extra $20 every month. It is true that WoW has a different sort of online play, in that there are ridiculous numbers of people on each server compared to what you get in TF2, but all that means is that there are a few thousand characters walking around that you will never care about or talk to, rather than 30-ish at the most. Imagine if Blizzard released DLC for Starcraft that cost you $20 a month and made a horde of ghost Zerglings that could not affect the game in any way run around your screen. Even the most passionate of Blizzard fans would think that they'd gone nuts. But when you throw it into an RPG, everyone jumps to your defence every time someone has the nerve to question the judgement of the mighty Blizzard, because how could they ever do wrong?2 things. First off you arn't throwing your money away. You are paying for a service. Think about how many television channels you get vs how much tv you actually watch in any given week. You pay for a lot of shows that you will probably never see.
... That went off on a bit of a tangent. Most of that wasn't aimed at you, by the way, it was just me being disgusted by humanity in general.
Anyway, don't do it. Even if you don't become addicted, you're paying a sizable amount of money for no real reason at all, making yourself sound bad if anyone ever finds out (because most people who know what WoW is automatically associate it with addiction) and may potentially cause other friends to join, which could end up getting them addicted and having them waste their lives playing that soul-destroying carrot-waving grindfest. That's sorta what happened to some of my friends; some people started playing, and because it has that addicting quality they would constantly talk about it at school, then other people started to play because the talk interested them or they just wanted to know what they were on about, then they get addicted, then you find that you're the only person there who doesn't like the game, because other people are 'only playing until I reach level 80' or 'really not that addicted' or whatever.
Just play a real game, one that motivates you to play it with good gameplay rather than an endless stream of pointless rewards that get replaced next level anyway.