This is not correct. He is either misinformed or feeding you a line.Mopar stage 1 from factory.
In 2003 the stage 1 kit included the 577cc injectors and the upgraded PCM.
For 2004/2005 the 577cc injectors came stock with the car, so the stage 1 kit was just the upgraded PCM.
They did not sell the SRT-4 with stage kits from the factory, ever. You had to purchase the stage kits separate.
Now he may have purchased it immediately and had the dealership install it with the car when new, but that would be the closest to "factory" as you could get.
If it is a true stage 1 car, the PCM would have a sticker on it that states "Stage 1 Turbo" and a statement about not being used on pollution controlled vehicles.
Unfortunately to check this you have to remove the PCM as the sticker is on the backside, and sometimes the sticker has either been removed or fallen off, being now 17-19 years later.
As far as the price, prices have been going up in the last year or so on the online trader sites for the SRT-4 Neon, likely because we're reached that point where the "honda bois" type SRT-4s have been rodded to death or crashed, and there are fewer models left to sell, and they may be in better shape, hard to say.
It would be nice if the guy had some better photos, the engine bay looks terrible, the paint is bad, painted rims look cheap, aftermarket headlights, hopefully the interior looks better. I don't know where the car is located so hard to make a judgment on rust, but there appears to be no holes in the usual areas.
7k may seem reasonable based on what you see online, but given the wear and tear, I suspect the interior likely has some similar issues, I'd start at 5k and see where that gets you.