Ok so had pain in the a** to lvl my engineering so while searching few other forums I found this guide, this is not my guide. Tried to search for one here but didnt find it so I thought ill be a good gnome and share it with you guys.
As many of you know, Engineering is quite a pain to level up and very expensive towards the end. I, However, have found a way to get the last levels free. The only requirement is good social skills.
350-375 Engineering: Basically, all you have to do is find a 'new' level 70-72 and offer to make them a Hardened Khorium Scope. This is obsolete now as the mats are usually not on the AH.
435-450 Engineering:
1. Find a new level 80 (you can tell by the type of gear/ guild they're in)
2. Offer them a Gnomish Swiss Army Knife. Here is where your social skills come in. You're going to want to make them think that it will
save them tons of bagspace and reduce their farming time
3. Make THEM pay for the mats, all the while saying what a good deal they'd be getting.
4. Profit. Maybe even a tip :P
I know it is kinda awkward, but it worked for me