There's sales all the time. You'll be fine. If not on Origin, then you'll be able to buy a bundle in-store for a discount whenever there's a sale, or for dirt cheap from a CD key site.

The Game Packs and Expansions go on sale less often than the Stuff Packs, and often when they are on sale, the SPs won't be. But if you're vigilant you can get some good deals.

Okay, so confession time. I'm a former pirate who bought every pack over the course of about 6 months. I got Get to Work and Get Together for half price and City Living for free (Christmas present), and because I bought all of my SPs and GPs in bundles, and only when those bundles were on sale, I did the math and basically got one SP per bundle for free each time.

It's too expensive to justify paying full price (I may be a Maxis fanboy since the early 90s, but as I get older, I find it harder to justify paying for any AAA game for full price - I bought Fallout 4 for $20, for example), but if you can find a good deal? Go for it.