4chan bandwidth was 3PB last month.

4chan doesn’t use amazon web services.
But you can guess the price with it.

$0.030 per GB

1000GB = 1TB    1000TB = 1PB
$0.03 x 3,000,000(3PB) = $90,000

3PB is $90,000 per month by amazon web service.

https://aws.amazon.com/cloudfront/pricing/