BF sales are to remove depreciated and overstocked items normally. So that mean for example if you were looking to build a 'current model' computer, that be a Intel iCore based on the 6xxx series, they would be having 'sales' on BF for 4xxx series based computers and components (like DDR3 which can NOT be used on 'current' model computers, which can only use DDR4 for example).
The other half is a 'bait and switch' which is they have 50 iPhone7 to sell (for example) but they know they will get 2000+ customers, so they put between the doors and the iPhone all the 'other' Xmas gifts they can buy 'on sale' when they can't get the iphone.
Same happens online, so you know, they work off your emotions and influence the shopping.
Best source to find pricing for parts is pcpartpicker.com . You can compare prices and you will know in your local denomination including your TAXES you all pay over there for the items.
Last warning; MOST BF items are for AMERICAN sale ONLY. So ordering via the Amazon Brit page won't yield you the sale price.