RSorder is the most reliable site to purchase RS Gold (both OSRS and RS3). Based on my own experience (12 years of RMT as the seller and occasionally as a buyer) I have discovered that it is the safest site in the market. You can trade between other members, which means the prices extremely affordable, and transactions are far more secure. It's difficult to know where the source for the precious metal, however should you find a seller who is legitimately selling cheapest rs gold, it's RSorder or a different marketplace site. There are no stores online will offer something similar.