ViaMichelin website will give you the exact prices, to the penny.
Making best progress on the autoroutes? Going faster, probably.
In fact that is not quite as true as it might appear. Hack down a motorway, stop for fuel and / or at the payage barriers and chances are you will see the lorries you overtook grind their way past you at a steady 55 mph.
Get yourself organised. Pay for the payage by credit card, which will save faffing about for coins. Get in the right lanes, avoiding those that have a sign saying, 'No motorcycles'.
Get a simple peg to clip your ticket to the screen, while you clear the barrier. Then, pull over just after the barrier, to put the ticket and credit card away together, somewhere easy to get your hands on them when you will next need them.
Don't dawdle about chatting to your chums on fuel stops. Six bikes filling up can take up to twenty minutes. When you are stopped for twenty minutes you are not moving forwards, explaining why the heavy articulated truck (who has not stopped) passes you again.
Time your fuel stops to match up with lunch / morning tea / afternoon coffee stops. You will waste less time.
Colmar is in reasonable range of a day's ride from Calais, without all motorway at all. Be a bit more adventurous with your planning.
PM me if you want a route down to Dijon which you could adapt without too much difficulty.