I think its generally the case that people wildly overestimate how much they can actually differentiate between 'superiour, expensive' and 'pretty good, reasonably priced' quality on items like this. Once you achieve that pretty good level double blind taste tests stop showing significant differences. You're literally paying for the experience of spending more money. Nothing wrong with that, if that's your thing.
Olive oil is definitely something where you can go quite a bit higher than the cheapest brands (even the cheapest "Extra virgin" olive oil) and really taste the difference. Say, up to £10/£20 for a 1/2 litre bottle. Possibly higher, but I've not tested more expensive brands than that. Cheaper olive does have some flavour, but is mainly a carrier for other foods and tastes. Really good olive oil tastes absolutely amazing just dipping bread (or even a finger) into it.
I certainly don't buy such olive oil regularly, but I can easily tell the difference if I do.
