This study introduces two knowledge-related constructs (i.e., consumer competency and product knowledge) into online purchasing expenditures and then analyses variables (i.e., convenience, trust, and privacy) that have been discussed in existing literature in order to investigate how knowledge plays out in the online purchasing context. The findings, derived from the responses of 124 survey participants, show that consumer competency is the focal element of online expenditures. While convenient service is still one of the most important factors, trust and privacy do not directly impact online expenditures. It is interpreted that competent consumers, who are already determined to purchase something online, are able to locate trustworthy sites and make purchases from those sites; consequently, these issues that are traditionally considered important do not necessarily dissuade consumers' online expenditures, but may affect individual web sites. This study shows that consumers' knowledge about technology and the Web are the main determining factors for online purchasing expenditures.