In reply to stp:
Interesting choice of products:
Shoes - unless you're going for the exact model you had last time, you almost certainly need to try on for size. Even then, the same size and model can vary over time in my experience. If you're looking to try a different type/brand then you certainly have to try on, and ideally compare by climbing a few holds. This is where a traditional shop wins hands down,and paying an extra £20 is well worth while.
Harnesses - again if buying for the first time, then swallow the difference and go to a shop where you can try on a few and compare. They last five years (minimum), so again, even if you're replacing like with like,there's no guarantee that five years down the line, the same model will be the same.
Guide books - these are generic products, so you might as well buy from Amazon, and put the saving towards the extra you'll pay for the above bits.
Sustainable retail businesses have by and large realised they need an integrated related solution - so that might mean:
A 'bricks and mortar' shop for passing trade and the sort of purchase discusses above
An e-commerce store, properly supported with SEO and digital advertising
An Amazon Marketplace store, for generic products like the guidebooks
An E-bay store for low margin or clearance items