I'd go with Emesis's suggestion.
You'll be out the cost of one warcraft game initially.
The three new warcraft games will each grant a month of play time to an existing account, and they'll be cancelled after the two months (one month free, one month payed), so the subscription costs are a break even.

Another way of looking at it...
Just playing in the evenings and weekends, you can easily level 5-6 teams to 60th (within the RAF 90 days) if you want that many variations.
Without RAF it would take so much longer to do this.
You'll level 3x faster with the RAF, so how much per hour is your time worth?
I bet even if you valued your time at $1 per hour, you'll save more hours then the cost of one extra wow account.