Not really sure (which I HATE as an answer). Here is my current thoughts:
At time of purchase, they were 500 credits each, plus the host pin. If you figure a host pin is worth at least 2 buyables, that's 1000. So the total would be 3000. Then factor in that this was many months ago and that the 1/5 pin is not easy to get a hold of (in my experience) and I think that increases the value.
Hmm... not sure what is fair. Let me think about it some. Or if you have any further thoughts, let me know. A shopping spree would be fine, if we go forward with this.