Stealth aircraft arn’t invisible, but if you need to get within 50km to even know there is an enemy aircraft there while they can can shoot at you from 500km away you are not going to achieve much beyond slightly depleting the enemy missile supply.

Yeah, but in this scenario you're not sending continuous radar pulses out from your plane, because that would instantly give away your position. Electronic warfare stuff is still mostly classified, but I have to assume finding the enemy has long been a team effort, and now with networked warfare would be pretty seamlessly so. Which brings us to:

It also means that the enemy now needs advanced radars to be deployed every 100km to even know you’re there, as compared to deploying 1/10 the radars at every 1000km for the same effect. If you want the coverage to know where the enemy is above your country and not just they entered it, that goes up by the square ~~root~~.

That's true, but in a defencive war they won't have much in the way of fixed radars themselves. Meanwhile, the Gripen seems vastly more survivable on the ground than a whole airfield capable of operating the F-35.

Without a bunch of information that's classified and a bunch that might not even be available I can't calculate myself how those factors balance. And, of course there's the elephant in the room of if our F-35s would even be able to fly in this scenario.

As for cost, the main driving factor is that there are ~160 Gripens flying for 6 countries, and 1100 F-35s flying for 10 countries, plus another thousand or so on order by the US itself. When it comes to extremely intricate and complex development and tooling heavy devices like aircraft, economies of scale matter a lot.

Getting the Gripen E down to ~121m CAD was a remarkable achievement in economic efficiency, no seriously this was incrediblely impressive, that involved significant compromises for cost, nevertheless it doesn’t change that Lockheed Martin can sell a more capible fighter at ~117m CAD just by being able to have an actual assembly line and tons of spare parts.

Oh, okay. That makes sense.