does anyone know the consequences of simply refusing to proffer a boarding card?
I refuse to produce it on the grounds that it is unnecessary. Sometimes the staff say that they are not allowed to process the transaction without it, but they usually give in to get rid of you.
Of course, WHS now wants everyone to use their dreadful self-checkouts, in which a boarding card is a necessary step towards completion. I go for the counter, but if I'm forced to use the checkout I use an FR card from a previous flight, in the admittedly faint hope that WHS will get done for VAT fraud by using the same details mutliple times to reclaim VAT.
On the wider issue of airport rip-offs, I can never understand why anyone buys the over-priced tat that is presented in these places. And I was responsible for setting one up at a UK regional. We sold spirits, fags and smells in the "duty-free" shop (all flights were domestic or EU, so duty was included) at 120% or more of the High Street price and 70% mark-up. We even sold over-priced holiday wear as "duty-free" (75% mark-up). For some reason people thought all this was a bargain, and sales were fantastic.
Much of what is described as "duty-free" in fact is not dutiable in the first place, in the UK at least. In some countries where the airport(s) have "duty-free" shops, there is actually no "duty" on anything.
If you have time (as I do; I always allow far too much time to get to the airport and through security) you can have an amusing time asking the shop managers what the duty is that their products are free of, according to the banner above the entrance. Most of them don't understand the question. This goes especially well at LHR.