I don't know much at all about vintage cards so best wait for a user who does know about them to reply, but from the information on
this thread it's clear that the blue Golden Nugget is one of the most expensive, along with the orange. A completely sealed, pristine condition blue Golden Nugget is a very rare thing indeed.
If you waited for it to come up on Ebay, I'm sure it would cost you much less than $3,000. But it will take you a long time to find it on Ebay, and when you do there will be a ton of competition to contend with. The steep price tag is likely because of the convenience. I'd imagine the person who buys it is probably someone who needs it to complete their Golden Nugget collection, or near complete it.
I would definitely contact the sellar though, and ask for more detailed pictures before I splashed that amount of money on it. Hell, if I was nearby I'd ask to come and see it first before spending that. I could buy a used car for that price, and I would want a test drive before I bought it.