[Chris_Newton]

You might also like to look into the EU consumer protection rules, particularly the Consumer Rights Directive and its respective implementations in the member states and the UK. There is quite a lot of specific information that must be provided to customers during the buying process, and there are some serious penalties available if a merchant is found not to have done so.

In particular, if a customer might have seen multiple prices for the same thing around the time of purchase, for example on a pricing page checked on a phone and then on a checkout process completed on a PC, you would surely want to have solid evidence that the actual price charged had been clearly understood and accepted at the time of payment.

[abelr]

Absolutely! I remember reading this paper [0] about personalized pricing. The fact that personal data (an IP) is being used to inform prices has to be disclosed in the GDPR disclosure of a website. A very simple way to avoid a lot of those issues however is to have time-limited experiments in which 100% of Country's flow is directed towards one experiment (in the case of Corrily we keep track of which user saw what price when to insure the user will always see the same price).

[0] https://www.econstor.eu/bitstream/10419/205221/1/de-Streel-J...