Zenopus wrote in Holmes 1st print:There was one on Ebay a few weeks ago. It could've been yours for just $589....!  


** expired/removed eBay auction **


Seriously, I haven't tracked these in years, since I bought my copy - just a worn rulebook with writing and missing the reference sheet.

The scarcity may reflect the size of the print run:

Frank Mentzer on Dragonsfoot in 2008 wrote:
Before '77 a large print run in gaming was 10,000. A huge run was 50k, and iirc that's what 1st print Holmes was, maybe 2nd print as well. Most of the reprints were 100,000 each (I think Law mentions this in Heroic Worlds) except for the last one (down to 50-75k iirc since TSR was planning a new version). [Source]

Looking at Heroic Worlds, I do see a mention of the Holmes Basic Set generally being printed in runs of 100,000 on page 26. The print runs for this number are not specified. Perhaps the first print run was even lower than Frank recalls, only 10,000?

Some trivia about the first print:
The 1st print was sold for at least six months, from July 77 to Jan 78 (date of the 2nd print).
The first sales were at conventions in the summer (Origins, GenCon) - thanks to Jon Peterson for finding evidence for this.
The first advertisement in Dragon was in Sep 77; the next in Jan 78.