As I've mentioned in the introduction, Engineering isn’t a particularly good profession choice at the earlier skill levels if you’re in it to earn gold. But, there’s still a market for the limited selection of items we can create that are useful to others, and the profession redeems itself somewhat post 300 skill.
A warning; If you plan to mass produce any given item with the intention of selling it in the auction house, keep in mind of supply and demand. Check the AH first, to see how many of that item are already for sale. Note what theyre being sold for, and figure out whether you’ll actually be making a worthwhile profit should you sell your items for that price, factoring in the cost of any bought ingredients.
Start off by making a few, and seeing how quickly they sell. If all goes well, you can make more. Make sure you never have a gigantic amount of anything. You won’t be selling 40 scopes in a night, and overloading the AH has a bad effect.
Also, there are always people watching what goes on in the AH, so be careful not to alert anyone when you spot a good market opportunity.
Let me give you an example of what I'm talking about here:
At some point in time, long before BC's release, I was looking into possible ways to make some money with engineering. I decided to check out the pricing of fused wiring in the AH. There were none up for sale, so I checked again the next day.. and the day after.. As I didn’t see a single fused wiring in the AH for over a week, I decided to make a bunch of dummies and sell the wiring I got from looting them.
At first I was raking in a crazy profit (I sold several for 12-14g each) for over a week, never selling more than one or two at a time. After a while, someone took notice of this and also started producing and selling fused wiring.
As time passed, the amount of wiring being offered by more and more people in the AH increased greatly, up to the point where the profit you’d get for selling one barely outweighed the effort and cost of making dummies.

This scenario is likely to happen when anyone discoveres a ‘new’ or forgotten product to sell.
Making your profit as big as possible before other people find out whats going on is key.
Any item available in large quantities in the AH on a daily basis should make you think twice as to whether it would be a good item to make a profit with. Still, check out the pricing on ingredients and see if you may be able to squeeze out some gold.
Schematics With Potential
So, you want to know which schematics are moneymakers? Read on! I have ordened all the potentially sellable items by skill level and given them a rating. Note that items that cost more to make than they would sell for are not present in this list.
The classifications ranging from poor to great are a result of combining the expected profit with the desirability of the item. Some items can net you good profit, but just don't sell very fast.
Exact profit amounts are not included in this chapter due to the often sizable price differences in both mats and finished products from server to server.
0 – 75
Sadly, there are no schematics worth making for profit in this tier of engineering.
75 – 150
Mechanical Squirrel(105)
Average: This is the earliest non combat pet you can make as an engineer. It sells reasonably well. The schematic is a random world drop, but is easily obtained in the AH.
Deadly Blunderbuss(105)
Good: Used in a quest in Ashenvale, many people pick one of these up in the AH.
150 - 225
Discombobulator Ray (160)
Poor: These can be hard to sell, but can make you a small profit.
Accurate Scope (180)
Good: This is the most profitable schematic for this tier of engineering.

225 - 300
Sniper Scope (240)
Good:This is a rare schematic. If you are lucky enough to have it, you can make a nice profit from selling these scopes. This is easily the best moneymaker for this tier of engineering unless you happen to have the Biznicks Scope and the mats to make them.
Tranquil Mechanical Yeti (250)
Good: You can sell this non combat pet for a sizable profit, but items of this type are not terribly quick sales.
Lifelike Mechanical Toad (265)
This schematic is extremely rare and the pet it crafts is nothing special. I don't know how well this one sells, but I have yet to spot it in the AH.
Fused Wiring (275)
Poor: Fused Wiring can get you a small profit, but takes Delicate Copper Wire to make. The wire is crafted by Jewelcrafters and isn't generally found on the AH.
Biznicks 247x128 Accurascope (300)
Great: This schematic drops only in Molten Core. Seeing that this zone is hardly ever raided by anyone these days, it is very hard to get. It is also hard to obtain the materials required to make this scope, as some of them only drop in MC. If you do have it and you can get your hands on the materials, this can net you a lot of gold.
Arcanite Dragonling (300)
Unknown: This schematic is a very rare drop from Cobalt Mageweavers (57-58 elite) in Winterspring. The trinket isn't very good at level 70 anymore and has lost much of its appeal. Its sheer rarity may make engineers that don't have this schematic pick it up, but I wouldnt expect much of a profit here.
300 – 375
Fel Iron Toolbox (325)
Average: Simple to make and should make you a small profit.
Adamantite Arrow Maker (335)
Average: These are very simple to make and require few mats.
Crashin' Thrashin' Robot (325)
Average: If these sell, they can bring in quite some gold. Actually getting them to sell is the tricky part.

Adamantite Scope (335)
Good: These scopes are easy to make and don't require any exotic materials. As with most scopes, there is always a demand for these.
Mana Potion Injector (345)
Average: Somewhat risky due to the high deposit of 3 gold for 24 hours in the AH. Remember you only get the deposit back if your auction is a success. Its quite easy to see your profit evaporate on deposits on these.
Stabilized Eternium Scope (375)
Great: These require quite a few mats to make, but they are the best moneymakers for engineers in this skill tier. Downside? The schematic drops from Attumen, the first boss in Karazhan. Its not a very common drop. Note: If you are planning to craft a bunch of these to sell, keep in mind that you might just spend ~5 minutes smelting ore per scope. I'd buy bars wherever it wouldn't impact the profit too much.
Gyro-Balanced Khorium Destroyer (375)
Good: Every engineer with 375 skill can train this schematic in Area 52. Considering the huge amount of rare and expensive materials required (including a primal nether), they must be sold at a steep price. In my experience, these guns are not quick sales by any means, but can net you a sizable profit.