This kind of optional extra often comes with a monthly fee or maybe a variety of monthly fees depending on whether you only want to use it on one site or several sites or unlimited sites. Of course, the pitch is that you'll want the unlimited version once you find out how much extra money you're making and the special price won't be there when you come back.

Time limited offers may be limited and "dime sale" pricing (where the price rises every few sales) make things appear scarce.Sometimes that's true, sometimes it's a white lie such as "only 100 copies will be sold" - I steer clear of promoting products that claim this when I see stats that show it's an understatement. Often it's a ruse because the promoter knows you won't ever buy if you leave the page.

It's best for the long term value of your wallet if you subject this kind of offer to an "overnight" test.Leave the page open in a browser tab and come back to it tomorrow morning. Press the refresh button to see whether it's still available (probably!) and, if so, what the price is now.

If it's not very popular, the price may have gone up a few cents. If it's stunningly popular there's a good chance the author will have put in a temporary price freeze to protect their profits (otherwise the price would have stretched beyond most people's wallets.