I buy and sell skill-books, faction/deadspace/officer mods and implants covering all 5 major trade hubs (Jita, Amarr, Dodixie, Hek and Rens) plus several regions that don't have a major trade hub. I play fairly casually and update orders infrequently, often going several days between posting/updating orders. Some characters get updated more often than others and I update sell orders more consistently than buy orders.
In July I made 22 billion after expenses (exactly the same as in June). Not bad considering the time I spent playing the market was way down, I lost 3 billion to an input lag induced typo and my expenses were up too.
Expenses were up because I bought and fit a bunch of ships for various alts to fly (Tengus, Prowlers, Cheetahs and Buzzards mostly) plus I've been going through nearly 3 times more PLEX the last couple months with 12 accounts now and 4 or 5 dual training.
My market activity was way down. I mostly just concentrated on 3 items and let the rest of my orders sit for almost passive income. For the most part I logged onto 1 buyer on Jita and couriered items to 4 other traders for sale. I did log onto other characters several times to post stock that was piling up and updated most of the orders on all my traders at least once during the month (3 or 4 times on several). I spent a grand total of about 20 hours working the market.
That's my actual current total net worth, I don't pad the numbers by counting ISK I've earned but have since spent and no longer have. That'd be like calling myself a real life millionaire because I've earned over a million dollars during my life when the reality is I've never had anywhere near a million in total.
Next month I'm going to try to keep the time under an hour a day and concentrate on 13 items instead of just 3 to see how that works out. I also intend to spend some time developing the implants market which has always been my 3rd and least profitable market, after mods and skill books.