Ok, sorry, didn't saw the source. My respectful excuses.
Very interesting. Yes, probably 150 aircrafts, that the standard number for AdA
interceptor / air defence role as I said earlier - it matches the numbers of Mirage IIIC, Mirage F1C, Mirage 2000C
+ the -B two seaters for operational training (and air defence, too, in the later types. The III-B could not, the F1B could a little, the 2000B was fully capable AFAIK).
Going to 300 or 400 aircraft mean covering the entire ground attack role.
In the case of the F3, that would not happen (unfortunately) because the Mirage IIIE fleet was still "fresh" while the Jaguar was coming fast. And later, the ex-Israeli Mirage Vs. Those three were the FATAC (Force Aérienne Tactique = Tactical Strike Command) backbone until the 2000D/N and the F1CT entered service, after 1985.
So ok, we agree about an early batch of 150 Mirage F3 for AD, at the cost you calculated. What we can do to lower the unit cost, and produce more aircraft, is to get the British (RAF) and Aéronavale onboard.
The F3, particularly with a big, powerful Spey, could replace a whole bunch of aircraft in RAF service.
As for the Aéronavale, Etendard IVs & Super Etendards were build in similar numbers: more or less 70 machines. And the Navy bought 42 Crusader.
So 100 aircraft for the French Navy. According to Liébert book on the Mirage, performance-wise F3 with a Spey is exactly what the Aéronavale seeked to replace the Crouze between 1967 and 1974, when they got Super Etendard instead.
A 10 tons thrust Spey + an aircraft a little bigger than the F1 = max power within weight limits of the Clemenceau catapults performance (max 17 tons at 110 kt, from memory, very rough aproximation).
What just occurred to me is that in this peculiar AFVG universe, the Jaguar may abort into the AlphaHawk (you guess, a subsonic Hawk / Alpha Jet build by all thre countries).
If the Jaguar is cancelled, then the F3 can start eating the ground attack role, and get past 150. The Israeli Mirage V are probably sold to someone else (Argentina, only a few years earlier than OTL, and not worn out by intense Israeli use).
Then the Mirage IIIE fleet needs a replacement but only after 1980 - the role taken partially by Jaguar and mostly by the F1CT and 2000D OTL, in the mid-to-late 80's.
There are two slightly different roles - clear weather attack and all-weather attack. On paper, the Mirage IIIE is the all-weather type, with terrain following radar, somewhat a French F-105... with the same default: single pilot work overload.
The clear-weather attack types are the Mirage V, as for the French Jaguars they were somewhat... in-between, as shown in Gulf War One. LGB, a little, but no IR seeker.
Truth is, all-weather / night attack had to wait the Mirage 2000D and F1CT, in the 90's.
Hence I can see a ground-attack F3 taking, first, the clear weather attack role with limited avionics (probably the IIIE) and one pilot. This would kick the Jaguar and Mirage V away. LAter a two-seat F3 can be developed with the 2000D Antilope V. Well, Antilope terrain following radars were flight tested from the late 60's on a Vautour and a Dassault Falcon.
n the end I can see the F3 pulling a Rafale, but gradually and mostly "by accident" and not planned from the very beginning. By "pulling a Rafale" I mean "replacing every combat aircraft AdA + MN +/- Mirage IV nuclear bomber" (Rafale did the later, the F3 was too small, although the 2000N... well, maybe).