The thing is, 3.8 million per day per slot boils down to just 158K per hour per slot. There are a number of T1 products that make 8-10 times that much per hour per slot, and it's dreadfully easy to find T1 products that break at least 400 or 500k per slot per hour. They're much easier to produce, since you don't have to bother with invention, and most of them have extreme demand. I'm really beginning to think that my invention slots would be overall losers if I used them.

Yes lets all hold hands on the wrong side of the market spread and wonder why we aren't making any profits. Poor criteria.

volume buy orders are only rarely made by procurers intending to use the item, most are made by people intending to reproc the item. Therefore there is NO competition to lift buy orders beyond reproc.

For the record, I doubt many objects will stand full time 24x7 manufacturing without you so annoying other market participants that the price marches down to 2% above reproc either. ie if you wanted to see those profits per slot, you would have to have far more than 10 prints being rotated through.

For the lines I run, I get about 3mil an object, and the objects take 2.5hrs to build.

Customs Office Gantries. (Or at least they do off and on. That market is saturated atm.)

If you sell to buy orders you are doing it wrong, and no wonder profits are bad for you. It may be trade profit but it is trade profit in YOUR pocket, not someone else's.

Off the top of my head I can think of two T2 modules that I've been selling since I started building T2 stuff, which are still selling at a great volume and a great price.

One of those modules, I couldn't sell in Jita if my life depended upon it. However, for an unknown reason Rens customers are willing to pay me as much as 300% profit, and purchase them at a decent rate with only a few other competitors.

The other module I can pretty much sell in Jita as many as I can manufacture. Typically making about 75m/day profit, so about 2.25b/month. This is with only one character that can build T2.

Chances are the problem is not "the system" nor the market if you are not making similar earnings.

That is incorrect. Trade profit buys you the spread, aka buying from buy orders and selling to sell orders. You should always be buying from sell orders and selling to the same type of order for manufacturing, this means you are getting no benefit of the spread, thus it's not trade profit. Your example is incorrect, there is no product in the universe where you can buy it from a sell order and then sell it to a sell order and make a profit (well, unless the market spikes).

Buying from sell orders and selling to buy orders is LOSING you the spread. Don't get me wrong, I see why you do it, it's a LOT faster than maintaining sell order, and often can make you more profit anyway if your cycles are quick and the spread isn't big.

Always buy/sell to the same type of order to get the manufacturing profit.

Edit : To be clear, I would never manufacture anything with such a thin profit margin that I'd lose money if I dumped it to buy orders, I always retain that option if I don't want to spend the time putting them up to sell orders. So really, it's no skin off my nose if you want to call some of my profit trade and some of it manufacturing. I think you're wrong, but we're just using two different definitions and criteria to reach the same end conclusion anyway, so in a real sense it doesn't matter.