I happen to agree with him more than disagree. Maybe not $3500, but definitely >$1000 and maybe $2000-2500. The Wild One is one of the quintessential biker movies... but there are basically NO motorcycles on any of the posters! Here are some images for comparison:
1953 US 1-sheet -- Marlon in lipstick looking at disembodied feet? WTF?
R1960 US 1-sheet -- Same as above with shittier colors, ugh.
R1960 US 40x60 -- Snooze. Same, same. At least it has slightly better colors...
R1960 US 30x40 -- Getting better I guess, at least there are motorcycles. No Brando. Looks like a bunch of cold (those scarves!) keystone cops...
R60s French 1p -- You can't even rely on the French, who usually knock them out of the park during this time period...
So what about the style B R60s from Antiques Roadshow? WHOA!
Motorcycles -- check!
Brando -- check, although admittedly not his best representation given the normally crude format/art on these 40x60s
In signature hat, jacket, and jeans (before they were cool) -- check!
Ready to beat some ass with a goddamn crescent wrench -- double check!
Given the other options out there, this would definitely be THE poster I would want from this title. The only thing that comes close is the later release UK quad, but that is photographic.