It is somewhat true. There are limits on prices of pharmaceuticals (Health Service Medical Supplies (Costs) Act 2017). There is also Article 102 of the Treaty on the Functioning of the European Union:
Any abuse by one or more undertakings of a dominant position within
the internal market or in a substantial part of it shall be prohibited
as incompatible with the internal market in so far as it may affect
trade between Member States.
Such abuse may, in particular, consist in:
(a) directly or indirectly imposing unfair purchase or selling prices
or other unfair trading conditions...
Prices (high or low) fall within the ambit of unfair trading conditions. See the case of United Brands:
charging a price which is excessive because it has no reasonable
relation to the economic value of the product supplied would be such
As spelled out in this article, one of the tests for this is is "the price-cost margin is excessive". However, the premise was that somehow a scientific definition of "unfair price" would be possible, but has not materialized. Note that this restriction applies to a concern in a dominant position, so a company with 1% of the market probably would not be subject to price-cost margin restrictions.