You could see this one coming over the past few months. With widespread belief that DC/WB is building towards making the Justice League a more mainstream property in film and/or television, copies of the team's first appearance in The Brave and the Bold #28 by Gardner Fox and Mike Sekowsky have been going crazy at auction recently.
To throw out one fresh example, a CGC 6.5 copy sold for $6111 on ebay yesterday. You could get a copy in that grade for around $3000 last year.
Now comes word that a high grade CGC 9.2 copy has been sold by Pedigree Comics for $120,000, far and away a record price for the issue in any grade. A census-topping CGC 9.4 copy sold for $60,375 nearly a decade ago. There are two copies graded CGC 9.2, two copies graded CGC 9.4, and none higher.
There's an interesting underlying dynamic going along with this, as DC/WB's current forays into film and tv continue to spin up: DC Silver Age keys are far, far tougher (along with being a bit earlier chronologically) in grade than Marvel keys are. For example, while there are only four copies of The Brave and the Bold #28 in CGC 9.2 or higher, there are 23 copies of Avengers #1 currently certified in that grade range.
I doubt this is the last record DC Silver Age sale of significance we'll have seen before the end of the year.