[SUTTON525]

If you are talking about overall by casting, not taking into any factors such as "painted/unpainted roof", short run variation such as "Cheetah base", and color such as the "Enamel White Camaro"... I would say the Superfine Turbine from 1973.

The a fore mentioned Camaro is my personal favorite.
With that said; I shy away from almost all "highly desirable" redlines.
Unfortunately, it's nearly impossible to verify the authenticity of such treasures these days.
Any talented custom or restoration artist can whip one up for you (complete with proper toning) in less than a weeks time.
This holds true with almost any expensive, highly collectible item be it diecast or anything else.
Buyer beware!!!

 

[SUTTON525]

How much are the nicer condition ones? I saw a few online that had good paint for about 15$. Is that what they're worth? ( not counting some super rare variation or whatever, just for a common one).

You ask a "loaded question". It all depends on the exact car being offered for sale.
I've purchased several very nice "common" redlines for $5 or less involving sales that were "face to face" over the years.
If you purchase anything on e-bay and have to pay for shipping you must consider a certain amount of price inflation.
My suggestion is to ONLY purchase redlines in person and from a reputable seller if you want the best possible deal.