British disposable household income is about 10% higher than in France (and note I said England first time around, which excluded the poorer nations ). In the case of the two ‘normal’ examples in the OP, ie excluding the business-class flight, the difference is about 20%. So I guess my explanation is halfway correct
French VAT is actually slightly higher than the UK’s (19.6% vs 17.5%). And there’s no import/export duties between EU members. Airport taxes will be the same no matter which country the tickets are being sold in.
Firstly the UK has a 17.5% sales tax called VAT, and taxes on some goods like tobacco and petrol are very high indeed, so although we have low income taxes the governement grabs our money anyway.
Also the examples given aren’t exactly representative. For instance I don’t know anyone who would pay over £2000 for a business flight to NY - any more than £1200 is a piss take (my last trip cost £800). This is especially true if you use the airline regularly.
Britain is pricey for some things but cheap for others.
A lot of them fled to the colonies and formed New England, where frugalness is still considered a virtue by many, which is why only the truely daring of us venture out to shop the day after Thanksgiving
). In the case of the two ‘normal’ examples in the OP, ie excluding the business-class flight, the difference is about 20%. So I guess my explanation is halfway correct 
