A CAP (Committee of Advertising Practice) report  at the end of July took Tesco to task for advertising a discount on some beer of a price that had been temporarily raised. This means you mustn’t claim you are discounting unless you genuinely are. I’m a big fan of dynamic pricing which can mean a price goes up for a while then goes down again and that could be perceived as breaching the CAP rules but only if you deliberately set a high price then tell people you’ve cut it. That’s not dynamic pricing, that’s conning people.
If you set a high price but offer a lower price for early sales or a discount for last minute purchases, that should be okay because the standard/full price is genuinely offered for a prolonged period of time. This is honest and transparent and shouldn’t upset the CAP.
If you have a set number of prices which you apply to seats in varying numbers according to demand, which is a crude form of dynamic pricing, that would seem to be within the CAP rules because you are not claiming to be offering money off.
However if you change the actual prices according to demand, which is true dynamic pricing, then you mustn’t claim that there is a full price which you are discounting because the truth is, there isn’t. Look to the airlines, the supreme dynamic pricers. Do any of us know what the price of a plane seat is? If we buy when there are lots of seats available, we expect to get a lower price; if we buy when there is a lot of demand, we accept that we will pay a higher price.
I think the problem will be for the many theatres in the UK who are stuck on giving all the seat prices in their print. I prefer to get people to want to see a show and then tell them the choice of prices. If this is too drastic for you, then only give ‘Prices from’ information. This approach is essential if you are practising true dynamic pricing.

Article Name
Dynamic Pricing Can Be Illegal
Dynamic pricing is all about putting prices up and down so what are the implications of a ruling by CAP makes clear that you can't put up a price just in order to discount it.