Flights from and to Paris form 1EUR + taxes only available for booking on November 3 and 4 for travel until November 30, 2021. The offer only works on direct flights so if you choose connecting flights you won’t see the 1 EUR fares.
Vueling Club members can earn Avios on these fares and you’ll earn a whole bunch 😉 The earn rate is 3 Avios per 1 EUR spent so you’ll earn 3 Avios each direction if you do score a 1 EUR fare each way. Premium member in Vueling Club? You’ll earn double that.
I didn’t do any exhaustive searching for the 1 EUR fares but from what I can tell is that with taxes and fees most of them will be in that 20 to 40 EUR range one way. Interestingly enough I found a fare even lower than 1 EUR – here’s Paris to Bologna, Italy for only 0.05 EUR before taxes and fees: