A common mistake made by advertisers: they approach networks and ask them what their CPI is. The networks provide some estimates, then advertisers compare them and eventually decide that this network offers lower install price than the other.
In fact, all networks utilize the auction principle: the higher the CPI, the greater the volume of traffic. Therefore, you can start a campaign with any cost. But of course, if you set a too low install price you will not get any traffic at all. Indirectly, CPI also affects the quality of traffic: the higher the cost, the more expensive sources you can buy, the better the traffic.
Rule of thumb here is to start with a competitive but not high CPI and then monitor the results. If you don’t get sufficient volumes of traffic, you can gradually increase the cost. But keep in mind that no network can pour traffic on your mill the next day, they all need time to warm up.
From country to country, CPI differs greatly. For example, in the US or UK the install price can be five times higher than in the developing regions such as Brazil or India.
It is also important to understand that different types of applications have different CPI, and that difference can be multifold. If you do not know the competitive install price on a particular market, ask a number of networks to share an adequate estimate with you and start with the one that is closer to the lower limit.
After you decide upon the cost, offer equal conditions to all networks you plan to work with. Otherwise you will not be able to compare their performance.