Most gold selling sites hire very cheap labor to do their work for them. Often these are underpaid, overworked laborers who live in sub-par conditions.  Hence the term "sweatshops".

Most gold selling sites multibox.  Multi-boxing is where numerous computers are being controlled by 1 person usually with the aid of automation programs aka "bots".  Dealing with such accounts will usually get your account banned in the span of hours.

Most gold selling sites advertise their wares in-game; thus causing a lot of chat spam.  Often times the accounts they use to deliver to you and the ones they use to spam the game are linked.  You can be banned for trading with such accounts.

Team Level Up's gold stock only comes from knowledgeable gamers such as you who farm gold.  Unfortunately the overhead costs of acquiring gold from players are at a much higher rate than buying them from sweatshops and hence the higher pricing.

Team Level Up uses only clean accounts to do the trades with you.  Our delivery accounts are never linked to gold farming/botting activities.  We have secure connection protocols and being based in the US, we have never been flagged.

We never spam our services on any game.  Being gamers such as you, we find it most taxing to be constantly spammed.  We employ several pay-per-click (PPC) campaigns to do our advertising for us.