Recently I've started gathering some EOD prices data for my testing. The first obvious place where such data is freely available is Yahoo Finance site. However I've noticed that many data providing companies sell this data, and not so cheap. So my question is: why would anyone purchase this data if it is freely available on Yahoo? One of my assumptions would be the data packaging (as Yahoo only allows you to download the data file-by-file) but then there are dozens of downloaders freely available on the nets. So do I miss something? Is this Yahoo data not reliable enough?

Recently I've started gathering some end-of-day (EOD) prices data for my testing. The first obvious place where such data is freely available is Yahoo Finance site. However I've noticed that many data providing companies sell this data, and not so cheap. So my question is: why would anyone purchase this data if it is freely available on Yahoo? One of my assumptions would be the data packaging (as Yahoo only allows you to download the data file-by-file) but then there are dozens of downloaders freely available on the nets. So do I miss something? Is this Yahoo data not reliable enough?