NotAeGirl941 I don't have any inside information on this, but I would point out that both Steam and EA offer Sims 3 expansion and stuff packs for $20 U.S. each when not on sale. EA has offered packs for as low as $8, but they're usually $10 during sales. The Steam bundle (all EPs, all SPs minus Katy Perry, no base game) reflects a price of $10 per pack minus a 10% discount. Expansions were originally $40, I believe.
Steam did use to offer the packs for as low as $5 each, and the bundle first had packs priced at $3.50, but I guess someone decided that enough people would pay a higher price to make it worth the increase. That's usually how these things work.
As for the price being unreasonable, this is just over four years' worth of content, so it's really not that bad considering everything included. It's certainly more than many people would want to pay, or could pay, but that doesn't make it inherently unjustified, especially when many players are still paying the current full price for one or a few packs at a time.