This character is not an alt but the main character. However, I DID spend a lot of time improving my engineering, mainly because I am in love with the high level headgear (especially great for gnomish warlocks).
And doing it -- yes, it is expensive. I took mining to support my "habit" and collected most of my own materials and sold stacks at the auction house. I found, however, that the best way to pump the stats is to make parts (blasting powders, gadgets, frameworks, struts) and sell these to vendors to recoup most of my costs. Making complicated items that require gems and lots of different components seems like a MAJOR financial burn. Why make goggles or a silver shotgun when you can get that ENG point by making a simple bomb or a bronze framework cheap?
I ALMOST ALWAYS leveled my engineering using the cheapest mats available. I could not have afforded to get to 205 making mostly complex items.
However, I also sold about a dozen Deadly Blunderbusses, five or so silver shotguns and a few goggles at the AH. While these did NOT make a profit, the helped offset the costs.
So, overall, I am disappointed. It seems then that I will have to be level 40 before I can attain 245 in Engineering. I was hoping for more like 35.