Can't help but jump in on this one as it is a question that is asked normally by people who have never built a car or have any idea of what they cost. Not hating here or trying to offend anyone, merely stating that the cost of a "built" car (almost regardless of style" is dramatically different than what most think it is or should be. It has been stated many times that you can buy a completed car for less money than build one, however you inherit all of the sins that are in the car. It is very tempting to build your own as it "seems" like you can do it cheaper and get the car you really want not to mention all of the fun you think you will have doing it. The reality however is that it is a lot of work, you have to remain committed and it will suck money like a tornado.
The answer to the question is simple; it will cost whatever you have and then some. If you try and do it cheaply, the car wont be right (might be for you, and you might be able to live with whatever isn't correct, however you will always know). They are never done and if you are a real car person you will always want to change something; its the nature of the beast. This is one of the greatest things about sites like this, you can look around for as long as you want to see what you like and what you don't.
Building a car is a combination of a lot of things to include money, tools, and skill. We have all seen a lot of cars with various things that made us wonder why something was done in the way it was (good and bad). By far the best advice I could ever give someone thinking about this path is this; first you MUST be committed to the project in that you lie awake thinking about working on it all the time. Secondly, develop a good plan and try and stick to it generally. No plan survives very long in detail because there are a lot of things that will change it (time, money, skill, availability, etc.). That said, having a good general plan will help make major decisions such as mods, drive train etc. This isn't to say that any of this won't change; in all reality much of it probably will (hopefully for the better), but you have to start with a concept.
To give you my personal example; I have been working on my 73 Cuda for about 9 years, it has absorbed over $39K and still needs at least another $20K minimum to be even close to done. This car has a stroked 340 (416), TTI exhaust, F&B 6 pac, homemade braking system (wildwood, viper calipers, etc), A833 4spd, homemade 4 link, firm feel front suspension, hot rod wiring harness, Neon SRT seats, Autometer gauges, etc. Could I have done this car for a lot cheaper? Perhaps but it wouldn't be what I want it to be. Despite the long amount of time, I still get excited about working on it and do so almost every day (at least 1 thing).
Could you built a nice car for $30K? Absolutely, but you have to accept certain limitations and have moderate expectations. I am in no way saying a $30K car isn't nice or an awesome car, rather I am saying it isn't the same as a $50K or higher car. Of course there are a lot of variables in all this; cost of the original car, talented friends, etc. If you don't have a car and want to get one to build, buy the best car you can that is as close to what you want as you can. This will greatly reduce the time and money you have to spend. Everything I have said above is why there are project cars all over Ebay; good intentions by someone met reality.
Just my $.02 based on building my 70 Challenger, 52 Dodge PU with a 330 Desoto Hemi and my Cuda. Last words; building cars in much like having children, the thought of it doesn't seem bad and in fact can ne quite exciting. The reality of it is vastly different but in the end I'd never change a thing with either of them.
