This is pretty interesting, where did you get the info from?
I maintain a thread
https://bitcointalksearch.org/topic/m.2250539 whose aim is to bring buyers and sellers of the holo errors together. The collectible marketplace is in the birthing stages. I'm hoping that providing a centralized place for buyers and sellers, and some historical price context for the various varieties of coins can provide some stability and definition to that market. Anything that makes a market easier to get into, and more well defined, should help the market grow, and in turn, values should increase. I think of the thread as an investment of sorts.
Anyway, there is a public app I've used to track the quantity of holo errors per type. I counted them up and saved them to a spreadsheet about a half year ago. I did it again a few weeks ago, and was surprised at how many had been used. I assume holders not aware of the collectible value, or perhaps redemption out of necessity. It opened my eyes to the inherent, increasing value through supply and demand both moving in the right direction for price increases.
If I feel motivated some day, I'll throw the result data into a public spreadsheet, so that the counts are more precise, and it would be easy to update.
Anyhow - the site is fun to explore. If I recall correctly, to get to some views, you have to change by changing the url parameters in the address bar.
