I've used GameTreeMac many times for my Mac game downloads and it's great because you only have to download a .dmg file once, no discs or origin needed (since origin doesn't work for mac anyway). For all Sims 3 games, you just register the game and it shows up on origin if you also own a PC.
They are currently running a deal as listed below:
Attention The SIMS 3 fans, we have the ultimate sale for you! Looking to complete your collections? Now is the time, because GameTree Mac is offering 50% OFF ALL The SIMS 3 Expansion Packs (Mac) for a limited time! Get all the expansion packs you've wanted, all at an incredible discount. Hurry, because this incredible sale ends July 4, 2012 at 11:59pm EDT.
The SIMS 3 Ambitions Expansion Pack (Mac) ONLY $14.99
The SIMS 3 Generations Expansion Pack (Mac) ONLY $19.99
The SIMS 3 Late Night Expansion Pack (Mac) ONLY $14.99
The SIMS 3 Pets Expansion Pack (Mac) ONLY $19.99
The SIMS 3 Showtime Expansion Pack (Mac) ONLY $14.99
The SIMS 3 Showtime Expansion Pack Katy Perry Collector's Edition (Mac) ONLY $19.99
The SIMS 3 World Adventures Expansion Pack (Mac) ONLY $14.99
