But OP isn't blind or poor-sighted so that doesn't apply here.
You are supposed to double check the amount before you put your pin in to make sure it's correct - that's what it was drummed into me to say to every customer when I worked in retail, and I do it every single time now as a customer.
Has OP clarified on that, though?! Even if she personally has perfect vision, I think we're still on potentially discriminatory grounds in general, as many customers will have poor eyesight. How could the retailer necessarily know?
In fact, IF he's particularly fond of trying this trick after pub closing time, plenty of his customers won't have their usual visual and mental processing faculties - and being very drunk is not an excuse to be taken advantage of in any way. If a drunk legitimately spent far more than they would do when sober, it's on them; but if they had placed a 'normal' order and been severely overcharged for it, I don't see how this could be considered in any way acceptable behaviour - especially by a presumably-sober trader.
I agree on the always advising customers to check the amount before inputting their PIN (although it could still be tricky if customers cannot see it) - but that tends to be the behaviour of an honest business that's trying to forestall any potential errors or cause for uncertainty, not one where that's their deliberate business model.
I highly doubt in this case that the pizza man urged OP to check the amount before inputting her PIN. Surely you'd also expect him to check the amount as well as the customer and to have said "Wait a minute - £65 for one pizza?!, that's not right!" For all we know, along with the contactless and the CCTV, some of the diodes (or whatever they are) on the terminal screen might also have been 'not working'!