At this point of tike there is 14 stuff packs, each cost 10$ that would 140$ for stuff packs compilation and you would hardly get enough content to expand on the base game and keep you interested for ...
I agree they're not cheap, but they do make a lot of difference in the game, at least for me. And honestly, if you buy all dlc at once of course it will be extremely expensive, considering we have 5 years of content. I don't think that's a very good point.
I have all the SPs and didn't spend $140, cause 1) sales 2)bundles.