The premium on a 25 has historically been low, even when BTC was in the $200's.  There's just not a big premium on the 25's and 5's, you'll pay proportionally much higher for the .5 and 1 BTC coins, and exponentially higher for the 0.1 silver.  The problem is that there's not too many people who can pop off purchase of a 25 today.  Back when they were introduced, yeah, many could afford them at the time.  Now with BTC where it is, very few would be willing to part with that much fiat to buy one, and anyone who has that much in BTC is not willing to part with that much of a premium.

Also, premiums are usually calculated in BTC, not tied to fiat or PM's, so a 0.5 BTC premium today will still be a 0.5 BTC premium tomorrow.  The only thing is what BTC is comparable to at that time.  So, it will be a very long time before that premium could be turned around to buy you 100g of gold, but either way it's still a 0.5 BTC premium.

If you want to sell it for the premiums mentioned, PM me.  It's worth that premium to keep someone from peeling it, but not much beyond that unfortunately.