Take for instance Germany. The federal republic increased their spend to $63.8b last year but that's still a shortfall of ~$27b relative to what a 2% spend would be.
Aggressive estimates (above official estimates) of the UK's (a similar sized ally) spending on Afghanistan in 2011m put the total figure at $26b for 10 years.
The cumulative shortfall in NATO contributions for Germany over that period is more than 10 times greater than the entire invasion and continued operations in Afghanistan during that period.
(edit: grammar and dollar signs)