A lot of times I use amazon simply because its convenient, but if its higher value I find out the product part number and search on that, and often will find it cheaper from a specialist dealer - IIRC my water softener ended up £550 or thereabouts from a wholesaler and was nearly £700 on amazon..
..remember if a wholesaler uses amazon, amazon are taking a percentage that he doesn't need to charge if he sells direct to you
+1And yet there is stuff I can buy in the UK *cheaper* than it is on ali-express.
People who have got the quantity discount...Ali express is also retail websites who mark up and ali-express adds a percentage on top of that...if a British company goes direct to the manufacturer in e.g. China and ships in 50, its amazing how cheap it is.