You also have to remember, $500 back in 1982 was a pile more maney than today, like they said...
$1:
The voucher values the evening at $500. Adjusted for inflation, that comes to almost $1,100 today.
No expiration date, I'd redeem it too. Although they did buy it at auction and they don't say what they paid, but still, the Planetarium offered it, they bought it, it's a done deal.