Believe it or not, you can save (and even make) gold just by getting to know people.
Nine times out of ten, someone is only a jerk to you because they don't know who you are. Maybe you're in a pug or you've accidentally (or purposefully) tagged their quest mob. While situations like these are tough to avoid and it's impossible to please everybody, it doesn't hurt to get to know some people. Through a guild or instancing and questing together, or even just talking when you're both up late night and no one else is on to keep you entertained, getting to know people can make you money. Let me tell you about a scenario that has kept money in my pocket for well over four months now.
I have a good friend who's a jewelcrafter. Many 80s can tell you right off the bat that JCing is a very good profession to have at level 80. This particular JC I've known since vanilla. She's a good friend and although we generally walk different paths, we've remained good friends (or gone in and out, depending on who you ask). Because I hit 80 before any of my guildies, I was looking for people to run instances with. My lazy and casual friends were taking their time, but this JC of mine moved up pretty fast. Her guild is a bit more towards the hardcore end, and a lot of their members wanted to gear up in epics as fast as possible. I was more than happy to run with them, and at a time when there were very few heroic groups moving and H-AN was just about impossible, I always had a place in their party, even as a "replaceable" dps.
There were only two things I did that kept me in that group. The first... was to always try my hardest. I top damage meters and I make it a goal to keep up with my past dps records and contribute as much as possible. Beating a previous sustained-dps record for a particular instance is fun for me! Now, no one expects dps to be any good, but the fact that I was very good was just a perk. The real reason they kept me around was because I was nice. That's it: I was polite, always said my pleases and thank yous, always checked if anyone needed some refreshments, kept everyone buffed, and made quirky jokes (the only kind of humor I'm good at). Over all, I made everyone's life easier by taking care of myself and helping to take care of the rest of them.
Now how did this earn me gold? I can list a number of ways right off the top of my head. First of all, I got emblems which helped me to get new gear without buying Bind-on-Equip items from the auction house. That right there saved me 100-700g for each equipment slot. Also, I got money and vendorable loot from the corpses in the instances. I also rolled on the frozen orbs and received dream shards when I didn't get any loot.
Ah, an enchanter in the group. This brings me back to the mention of professions. With both an enchanter and a jewelcrafter on my good list, I had life made. Now, I could acquire the raw gems and I had someone to cut them. The JC was able to achieve exalted reputations with the instance factions and learn the rare-gem recipes quickly because I had helped her through the heroics. Ah, runed scarlet rubies reflected in my eyes! At 5g a tip and a slot in my helm, necklace, shoulder, cloak, two in my chest, bracers, gloves, a belt slot, and then two in my pants and one in my boots, I saved 60g right there. In the end, I'll save much more as I replace my old gear and need more gems.
And now that I was on the good side of an enchanter, I had someone who would accept my greens (mailed to her 12 at a time) and disenchant them, taking a very, very modest cut for herself each time. Anyone will tell you that you make much more money off of auction-housing enchanting dusts and essences than vendoring greens.
Every now and then, when I proc an alchemy mastery, I'll send either of them the bonus. I have friends to talk to whenever I need, and they've made me more money than they've cost me. Keeping them happy is not only a small part of the business, but something I would do even if their professions didn't work out in my favor.
It pays to network.