Until recently, NOIs had to be filed manually, by paper and under a prohibitive pricing structure. So if you started a service and had the publishing data for say 5 million songs, but did not have the information for another 500,000 songs, the service would need to file NOIs, saying it is licensing and using those songs with the Copyright Office. That process would cost $75 to register for the filing of all those songs, and $2 a song, or about $1 million. Also, the NOI for each song would need to be filed individually, although they could all be batch delivered to the Copyright Office.
But about two months ago, the Copyright Office revamped the way it is willing to accept NOIs and changed its pricing structure. Now, NOIs can be filed on excel spreadsheets, with something like 20 columns of relevant data needed to be completed for each song. This electronic filing still requires an upfront fee of $75 but it now only costs 10 cents a track. So now, filing NOIs for 500,00 songs will only cost $50,075, instead of $1.000075 million.
Source: U.S. Copyright Office Clears Path for Digital Compulsory Licenses | Billboard