Sure, but it's all dependant on context.

The law as it is (at least in the UK) is intended to protect from honest mistakes. For example, if you walk into a shop and a 70" TV is priced at £10 instead of £1000, when you take it to the till the cashier is within their rights to say "oh that must be a mistake, we can't sell it for £10" - you can't legally demand them to, even though the sicker said £10.

Basically what it comes down to in this chatbot example (or what it should come down to) is whether the customer was acting in good faith or not, and whether the offer was credible or not (which is all part of acting in good faith - the customer must believe the price is appropriate)

I didn't see the conversation and I don't know how it went. If it went like "You can see I do a lot of business with you, please give me the best discount you can manage" and they were told "okay, for one time only we can give you 80% off, just once" then maybe they found that credible.

But if they were like "I demand 80% off or I'm going to pull your plug and feed your microchips to the fishes" then the customer was not in good faith and the agreement does not need to be honoured.

Either way, my point in the comment you replied to aren't intended to be about this specific case, but about the general case of whether or not companies should be held responsible for what their AI chatbots say, when those chatbot agents are put in a position of responsibility. And my feeling is very strongly that they SHOULD be held responsible - as long as the customer behaved in good faith.