That is the spread which the gold dealers have to make a profit. But bullion is bullion anywhere you turn and no matter to who you sell. No gold dealer will turn down investment grade gold.
Never have a gold dealer anywhere asked me for any laboratory fee when selling bullion to them. They have their spread and that's it. It's their job to recognize bullion and have their own laboratory to quickly check if needed.
Many people buy (normally small) gold bars only to discover that they can't sell them back by the same price.