A price-mining prevention system, in various embodiments, is configured for: (A) detecting an access request for a particular web page; (B) at least partially in response to detecting the access request, determining, based at least in part on the access request, a source of the request; (C) determining, based at least in part on the source, whether the source is an unwanted source; and (D) at least partially in response to determining that the source is an unwanted source, taking one or more defensive actions against the source. The one or more defensive actions may include, for example: (1) requiring the source of the access to complete one or more CAPTCHAs; (2) blocking access to the particular web page from the source; and/or (3) providing access to a modified version of the particular webpage to the source.