Anyone else calculate estimated value vs purchase price for game collections?

[retrogemcollector]

I have an Excel sheet for the past three years and I constantly updating at least once a month.

[bikingjahuty]

I did this a while back and at the time I averaged about $10 per game in the collection. Keeping that average, my collection is probably worth between $15,000 and $20,000. As far as how much I've put into it, it's probably about half of that. I amassed probably 70% of my collection of the cheap. The rest is a combination of retail and ebay prices.