One of the problems with cost is the idea should be to start off in v8's, then f2's then progress into f1's as sponsership / budget allows. This dosn't happen because V8's and F2's are formulas in their own right and especially in F2's some with bigger budgets spend more on their cars than others. It's only because there are clashing meetings ( sometimes 3 on the same day ) that means F2's don't have quite such an issue with cost.
All I would say is how much more can be spent on a F1 than today? there are limitations surely on what else can done and what i'm seeing is a much leveller playing field, with yellow tops getting machinary to race with the superstars, Ian Brickley has a new car I believe.
Surely if there are a band of 40 - 50 cars who regularly attend meetings and they're reasonably evenly matched then there's no problem. You don't need 400 drivers to make good racing. Once the field is level, then we'll see the "crash and bang", element of bangers maybe.
I agree that most F1's look the same, but so do F1 grand prix, Nascar, Formula 3, indy car, etc. The look of a modern F1 stock car is unique, something which grabs the attention, promoting the sport by it's appearence, especially with the big wings.
Drivers don't attend meetings for their own reasons, not just cost, the fence at Sheffield so I believe is one, a wife and family is another and my old favourite, ONE meeting a week is enough ( wait for the outcry ). Maybe driver and spectator numbers are more linked then first appears, I am only doing Sunday at Northampton not both.
Success needs a combination of good hard racing ( already there ), meeting presentation ( getting better ), good advertising / promotion ( also improving, and the thing that's missing, the WOW factor - speed, bumperwork, noise, colour, crowd participation ( cheers, boos ), in other words Value For Money.
We shouldn't be trying to save save save, we should be encouraging people to spend their money but be thinking money well spent. That is where the problem lies currently.

One of the reason for the decline of audience is the fact that the sport is not as available to drivers and fans locally as it used to be. The decrease has been more prominent since the losses of Bradford, Long Eaton - a ten year gap at Belle Vue and so on - To be an avid F1 stock car fan is to a degree way beyond the average person given the dedication to travelling and is no longer accessible regionally regularly enough to create in many areas a crowd base.

Racing is generally good - but - why are promotions now increasingly desperate to get huge amounts of cars on track these days - To provide action - the flip side of that coin is obviously potential damage and cost of and perhaps we do need to address the core problem and seek to reduce costs - I can see the first 50 car race looming!

As you rightly say, one meeting a weekend is preferable which means to achieve that the sport will need to contract even more - which in itself will bring consequences further down the road as a lack of local racing will as has already happened to a big degree, man a loss of some drivers - and inevitably fans.

There are no easy answers and I guess market forces will dictate the future of the sport rather than the NASCAR style.