A VERY honest review.
I've used G2G, Playerauctions, and Kingboost.
I've been a top player in WoW when it comes to arena and raiding. How? I paid for it. That's why this is going to be posted as anonymous. I've spent THOUSANDS of USD getting top on the Blizzard and Raider io leaderboards via M+ and raiding, and I've used all three of these sellers.
G2G: I actually argued with a few sellers over what I wanted in a boost. I'm the one paying, I should have it tailored. If you're not buying cheap Discord nitro's from G2G, avoid. I never could make a deal with any of them. Plus, I've dealt with a lot of rude sellers.
PlayerAuctions: TBH Asian slop. I have nothing against Asians, but they can't sell for crap let alone most of the time I don't understand their poor English. I've had a few ghost me a few times. I suppose they thought I was being too complicated about what I wanted. Sorry, if I am buying a service, I want that service the way I want and YOU WILL do it how I want or I refuse to buy your service. However, I mainly use PlayerAuctions to buy WoW gold, it's a very simple process and they at least understand that; also it's very cheap.
Now let's talk about Kingboost. I've dropped over $1200 so far on KB. $400 of that was to get worlds top in arena when the season came out and now I'm buying boosts on other MMOs I'm playing. Here's what I LOVE about Kingboost; they're Russian. Why is that a thing? Well, they actually understand what I want unlike PlayerAuctions. It shows effort to understand and communicate to the buyer. It's very nice when both parties can fully understand another. I also cherish their occasional generosity. I had a booster once give me a bit more than what I bought because they were feeling generous. Will this happen to you? Maybe, maybe not, but I felt appreciated. The customer service, I'm pretty sure there's two of them that alternate, have been extremely nice and thoughtful of me. I've even had some bad days and they were right there. They also go beyond to make sure that you're happy. I've never experienced that before with any other service. It sorta feels like they're a friend. Kingboost may not be the cheapest service, but you're buying quality and that, to me, means the most; because spending your money and dealing with frustration, is fear. With Kingboost, when I spend money, I sleep well knowing my account is safe and Kingboost won't hurt my account or take off with my money (which has happened on G2G once.)
So, take my experience and use Kingboost. No service is perfect!!! Let go of that illusion. Sometimes Kingboost has day or two wait to find a booster for my order, but the boosters are quality and I've delt with boosters on every seller market. Hell, by this point, I have my own boosters that I wait for to become available. I've used Kingboost THAT MUCH over the past 2 years. Again, Kingboost isn't slop. It's quality.