I know someone with a small car hire company and they like to always quote a price lower than the competition.

Someone is implementing a cURL solution for them which queries the competitors prices, deducts 5%, then quotes that price. I guess the query will be run less than 5-10 times a day.

Sounds sensible, but is it risky? Do sites notice and care when their site is accessed like this (with a regular automated query)? Can they block the access? Get the site taken down?

Or is it more or less common business practice?