Cambridge University Press sells articles from its journals for about $30 each. But they have also introduced a "rental" system, whereby they will give you online access to the PDF of an article for 24 hours at a much lower price, typically $5.99. See here for an example. A rented article cannot be downloaded, printed or cut-n-pasted (details here).
I have not been able to test this service, because it depends on a java applet, and on my system this does not initialize correctly. I get a blank screen. I've tried both Firefox and Chromium. I'm using a correct and up-to-date version of java,This is an interesting model, and I think I quite like it. The abstracts of articles are available freely, so one can get a reasonably good idea of what is likely to be in the article without paying anything. It would be better to have page one also. The 24-hour access is interesting because it means you have to decide to read the article just before you rent it. You have a day and a night to read it. Sometimes I download an article but then never get round to reading it. The rental system makes that impossible. You can't keep it, and your time is running out, so it is likely that you will pay and then read the thing there and then, barring interruptions from your children.
java version "1.6.0_23"OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre11-0ubuntu220.127.116.11)OpenJDK Server VM (build 20.0-b11, mixed mode)running under Ubuntu, all very standard. It seems likely that CUP hasn't tested their new rental delivery system widely enough yet. CUP gives no warnings about any problems, nor any specifications about special systems or computer platforms that may be necessary. All they say is that you need a browser and internet access.
The price, $5.99, is nearly right, but it is still too high. It is a deterrent price. It effectively stops you browsing items that might-or-might-not be of interest. It kills serendipity, which is a crucial element of serious academic research. A reasonable price would be $3-$4, which in today's economy is a fair price for something that is likely to be only about 20 pages long at the outside, and usually of undetermined value to your research. Compare with emusic.com charging £0.42-£0.49 for a single track from a CD.