Tesco do this with a number of items, you have be observant.
I like this particular chilli sauce, so buy 2-3 once a year when on offer. This is not a mistake, it's down to Tesco keeping the smaller bottle with the sauces and condiments, and the larger one in the Asian aisle. Spot the difference!
The smaller bottle is always more expensive normally!
I've often spotted the same things in larger sizes and better prices in the World Food aisle and it's not just Tesco's that do it, they all rely on people not checking the unit price to see if it's a good deal or not. The other day it was 4 tins of baked v single tins, same make and size but the 4 tin was 45p more, I guess they hope those in a rush will just grab what they normally buy without looking!
Nuts and seeds are the same, they can be found in the snack aisle, World Food and fruit section, the same product in different sizes at three different prices, the World Food aisle being considerably cheaper and a bigger bag!
This happens so often and, as has been said, I think it relies on people 'grabbing and going'! And it definitely isn't just Tesco.
I spend ages working out the price per ml, g or whatever! I look things up on line, work out the best option and then tell Mr EB the exact item to buy.
I always buy my walnuts from Lidl - they are cheaper and much sweeter than Tesco's ones which I find quite bitter. Mixed dried fruit I buy Morrisons via Amazon pantry. It is a 'luxury' one with cherries, apricots and pears mixed in with the usual suspects. Will have to try Lidl's though as we only do Amazon pantry when buying dog biscuits.