Users can purchase books on a one-off basis or sell them to others via the web site.

An additional $19.3 million has been set aside to purchase electricity for Kosovo on an "as needed" basis.

And that meant that the colony could purchase its supplies on a just-in-time basis.

Memberships can be purchased on an annual basis.

Other services, such as word processing and clerical help, can be purchased on an individual basis.

Games are purchased on a game-by-game basis, which allows unlimited play of the game.

However, it increased the amount of silver the government was required to purchase on a recurrent monthly basis to 4.5 million ounces.

Another is the elimination of fuel which has to be purchased on an ongoing basis.

Individual articles can be purchased on a pay-per-view basis.

Released on December 15, 2010, the band allowed the track to be purchased on a name-your-price basis.