Speeding Tickets more Expensive Now?

Phone the nearest French Consulate to see if they can shed light on it. But it doesn't really matter in the end. You can imagine how far you will get disputing the fine with the department concerned in France.

Because fine levels change. In our local area all of the fines for the work zones were recently doubled because they wanted a bigger threat. If it is 90 today, who knows or cares what it was three years ago? Seems kind of silly to argue what others have paid.

The amount can also vary based on how many km/ h you are going over the speed limit. If you were going 12 km/ h your fine could be greater than someone who is going 3 km/ h over the limit. This might be part of what you are seeing.

What the fine was 3 years ago is a useless comparison.

I suspect the speeding fine in Phoenix is not the same as in Boise.
Each jurisdiction sets its fines.

What possible difference would it make? Are you anticipating that you might mount an equitability claim in the French court with jurisdiction over this matter? Traveling to France a few times, retaining a local avocat (the attorney kind of avocat, not the guacamole kind), all to argue whatever point you're thinking?

In other words, are you contemplating, probably vainly, to spend several thousand dollars plus time invested to knock down your speeding fine by 45€?

Doesn't seem like a good investment to me. I would recommend pulling out a credit card and paying your fine online. Chalk it up to experience, teaching you to maybe, just maybe, follow the speed limit the next time you drive in France.

"Phone the nearest French Consulate to see if they can shed light on it."
Don't bother if you are in the US and covered by either the NY or LA French consulate. As others have said, why the does the amount of the fine three years ago matter? Fines change and generally the rate increases. For example, parking violations in Paris are now significantly more than they were three years ago -- it happens. Speeding fines differ based on where you received the ticket and the speed of the infraction and things like if it was raining or if you were in a construction or otherwise reduced speed zone. In some areas of France, the minimum speeding ticket is 90€. Were you in or near a village, town, or city when you got the ticket? I once read that in "built-up" areas of France the minimum fine is 90€ but I don't have the time right now to look for that site.

Here’s a chart that spells out vehicle fines in France. The info on speeding is under minor offenses 3rd and 4th class. The fine is actually €135 or €68 depending on the class into which it falls. If it’s paid within a specific time period it can be either €90 or €45 depending on circumstances. Read the footnotes!

My ticket last year was 45 euros. Based on Phillips chart, that is correct because it fell into this category: "Breaking speed limit by under 20 km/h when limit ≥50kph" (and I paid in time for the reduction).

The following category is 90 euros if paid timely: "Breaking speed limit by under 20 km/h when the speed limit is ≤ 50kph". So that seems to be the answer. And notice that both categories seem to overlap at exactly 50kph.
So the answer is that you should pay ASAP to avoid an increased charge.

I found a French web site (http://www.securite-routiere.gouv.fr/connaitre-les-regles/reglementation-et-sanctions/vitesse) which explains the higher fine is because I was driving in a 50 km/h zone. Apparently, they double the fine in 50 and below zones, compared to above 50 km/h. The full fine is 135 Euro, but I get a discounted fine of 90 Euro if I pay early.

Interesting about the 50 zone falling into 2 categories with different penalty.

Wonder how which category is chosen when the ticket is issued.

When I received a speeding ticket in Spain it was for €100, but if paid on the website within a certain period it was only €50. Sounds like the same thing in your case.

Interesting about the 50 zone falling into 2 categories with different penalty.

I based that on Phillip's link, which was from an English source. Maybe there was a mistake in translation.
[Note: I just looked at the French link from the OP. Yes, it was a mistake in translation.]

So, pay the fine, chalk it up to experience, and move on.

Otherwise, don't pay the fine, ignore it, and never travel through France again. Come to think of it, never travel through an EU country again....

You decide....