i just want to say. I will always be an engineer! Even without making ammo psh. i never did that to make money - I just mine things to make money / do dailies.
If you really want to, the pet bombling and lil' smokey are now BOE so go make those for some cash.
Engineering is much more than that. How awesome is it that I can port to Gadgetzan, Toshley's Station, or Most of the zones in Northrend (wormhole) instantly?
I have a personal butler named Jeeves, and I also bring out my mailbox quite frequently.
Also having a AH in Dalaran is a huge plus so I can just park there and never have to leave for IF or SW or whathaveyou.
Out of my 3 80s - 2 of them are engineering. My new main thats a hunter, is already pushing 400 engineering at lvl 65. Plus with the Gnomish Army Knife, I have a way to rez people sometimes if it works too!
Plus at lvl 65 if you level up engineering to get the Frost Goggles of the.... (something like that I believe around 420 or 425) they're basically lvl 78 blue headgear that you can wear at 65!
Final words in a minor wall of text: Parachute Cloak!!!! Flexweave Underlay! That saves me so many times and makes it fun in game

That being said, I do not plan on making any money with Engineering, in fact I believe I have lost thousands of gold amongst all my engineering characters. But I do it for the love of fun trinkets/ thingys
Pyro Rocket is a fun way to get killing blows with as well. VROOM ROCKET!