Time... youre not factoring in time. My journey started around 10yrs ago, so not that long, but ive seen spot price dip to nelow £10 and peak over £20.

Spot price also doesnt take into account the price of a coin/bars price increase througg "collectability" over time. Coins i bought back in 2015 at £12/15 now fetch £30+, which is well above spot.

There are other channels available to buy silver to avoid stupid high premiums. Have you looked at the silverforum? Or group buys/direct buying from @backyardbullion.

I dont know why, but im assuming yourenin the UK?