A friend and I have been doing this for a couple weeks (well, I have anyway... he started a few days ago). I think he's still mainly doing the "regular" packs and I've mostly moved on to the Winter ones.
You definitely do MORE than break even, given enough packs and a little bit of time. When I buy a round of packs I never fail to get several more ATOs or Winter IOs than packs I bought, and the sales from those do more than break even. Boosters, catalysts, unslotters, converters, merits (= more converters), and Brain Storm Ideas (20 of which = rare invention salvage = 500k each) are just icing on the cake.
When I factor in the now near-endless stream of respecs, free costume sessions, amplifiers, and dual/team inspirations that all my characters will have access to, I just don't know why you wouldn't be doing this.
I don't even make as much as I could, as I lazily list all ATOs for a certain price and all Winter IOs for a certain price and take my chances that I'll get more than I list for (which I almost always do). If I took the time to look at each one's sales history and actually list it appropriately, I'd make more than I do.
It's NOT extremely fast and it can be boring at times (especially listing all the converters since you can only do ten at a time -- I've thought about switching to Boosters so it'll go quicker, but it's a huge pay cut to do that given enough merits), but for someone like me who's kind of lazy it's kind of nice to just log in a couple times a day and collect a few hundred million inf at a time.
The complaints I've seen seem to be from people only buying a couple of packs and getting unlucky. It definitely IS possible to not get any IOs for a couple packs, so if you're only buying a couple I can see that's disheartening (especially the Winter packs). But I promise you you won't lose anything if you buy a lot.
Until the market crashes, if that ever happens. :P