ROI for patent application

The ROI of a patent would have to be determined by the likelihood of the commercial success of the product/system being patented. For example, the cell phone, or when Apple came out with their iPad - apparently, the commercialization of tablets had been tried before, but were not successful, and yet when Apple came out with their iPad, they apparently had the know-how of how to successfully market their iPads, so their ROI was obviously huge.