Who ever talks down on Keyword Planner as an unreliable tool — is not being realistic. It is one of the most valuable and free tools for keyword research, and is used by professional and seasoned domainers alike. The suggested search volumes on Keyword Planner are estimates, and can be higher or lower than the suggested number. However, Google has a solid algorithm that gauges the competition (demand) of keywords among advertisers, and that demand (low, medium or high) impacts the suggested bid. The competition level and suggested bid per keyword are very reliable in determining the value of a searched term, and this should be where most of your focus should be; not necessarily volume. Think of it this way: Who are the potential buyers of your domains? Searchers or Advertisers? 'Advertisers target Searchers', 'Domainers target Advertisers'. Now, you get the picture. Good luck!