Well, $10 for stuff packs (the price in the United States) is actually quite low... especially compared to Sims 2 and Sims 3. Those stuff packs were $20... and they never even came with new gameplay content, unlike Sims 4 stuff packs.
Honestly, I think it would've been better if game packs just replaced stuff packs completely. When they first announced the 'game pack', I assumed it was meant to be a replacement... and I thought it was great! However, then they announced 'Luxury Party' and realized the game will continue being the cash grab it's always been.
As for the expansion packs, I feel like it just overall depends on which ones we're speaking of... for example, Seasons and Cats & Dogs, in my opinion, were worth $40 (US price). Get To Work, not so much... same with City Living. Then again, this could all depend on personal taste as well.
Though, I do remember when expansion packs were only $30 (Sims 2) and came with A LOT more content than they do now... as I've always said, Sims 2 was definitely the golden era of this franchise. In my opinion, that was when it seemed like EA actually cared more for its players... then Sims 3 (as great of a game as I personally think it is) turned the franchise into more of a cash grab (the store alone was very evident of this).