More cheap transatlantic flights coming
 

There is no such thing as a free lunch, but if $69 sounds "too good to be true" for a trip across the atlantic pond, it may or may not come close to a free lunch. Travel reporter Ed Perkins has an article at
http://Www.airfarewatchdog.com/blog/...es-really-but/
Huge "buts" for now, yet worth keeping an eye on.

Since the British tax is only on outbound flights, take the train through the Chunnel and fly back home from Paris.

True, except that the cheap fares the author highlights only apply to the UK-US direction, so obviously - as stated in detail in the article - the tax doesn't apply to those.

topping

It's not that unusual that low-cost carriers offer fares of less than the sum of taxes, fees or duties for a limited number of seats for promotional or marketing purposes.
I could fly from London to Berlin on many dates in the next weeks with Ryanair for less than what the APD should cost, i.e. less than 13 GBP.