The "gold" bricks we use are really goldplated. With real 24k gold.
This is something you won't be able to find anywhere else. Even the 'gold' bricks made in short batches by the LEGO® company are actually chromeplated in gold color.
The bricks are extremely hard to cover with gold since they are made with plastic. What makes it even harder is that we need the gold layer to be thin enough to preserve all the bricks details and at the same time strong enough to sustain wear overtime.