For years, the IAC (Canarian Astrophysics Institute) has paid the cost of visits to the observatory. Now they need to be even more careful with their money, and visitors will have to pay 9€ each (6.75€ for residents of La Palma), which should cover the cost of the guide and administrative overhead. The visits are still daytime only, and last 45-90 minutes. This includes a short talk on why the observtory is on La Palma, a visit to the MAGIC telescope, and for over-12s, a visit to the inside of one of the other telescope. This is most often GTC,the biggest telescope in the world, but it may also be the WHT, INT, or TNG.
You can book your visit here