If you are an app freak but do not like to pay highly for your apps, Appsales is a must for you. This simple app, just keeps track of all the apps which are on sale, even if for a brief period, and sends you periodic notifications, so that you can grab your favourite app at discounts which may range as high as 90% of their normal price.
You can even view the price history of the apps, so that you can decide when and whether to buy them at the discounted price. You can put some apps on watch so that you will be notified as soon as their price drops on the play store. You may setup your own filters, share sales with your friends and also get information on the other versions e.g., lite, professional, etc.
A very good app to monitor the prices of your desired apps.