How the buy/sell spread works
Every dealer quotes two prices. The distance between them is the cost of doing business, and it shapes how long you should plan to hold.
Two prices, one metal
A price board always shows a higher number and a lower number. The higher one is what you pay to buy. The lower one is what the dealer pays you to sell. The gap is the spread.
The spread is not a trick. It funds the assay checks, the vault, the insurance, the staff and the risk a dealer carries by holding stock while the market moves. A dealer with no spread would not survive a week.
What this means for timing
Because you cross the spread twice, once on the way in and once on the way out, short trading in physical gold is hard to win. The metal has to move by more than the spread and the premium combined before you are ahead.
That is the honest case for treating bullion as a multi-year holding rather than a trade. Over long periods the spread becomes a rounding error. Over a week it is the whole story.
How to compare dealers properly
Do not compare only the buying price. Ask for both sides. A dealer advertising an attractive selling price and a punishing buy-back is more expensive than one whose two numbers sit close together.
Swiss Gold shows both sides of the board on the site, and the website reads the same rate as the branch screens.