Adjusting for inflation, 10 dollars in 1979 would be roughly 42 dollars in 2023. An thus 15 dollars is roughly 63 dollars. Which is less than the current prices, certainly (a quick look places a 4-day pass at 135 dollars).
"A Letter from Gigi" was a satire/rumor/gossip column: Gigi D'Arn = Gary Gygax + Dave Arneson. It was written by T.E. & Chaosium staff, but with juicy submissions from others.
