Quoted for epicness. It should be sticky'd...Then again, no one reads the sticky's. Why do I say that? Cause threads like this are created at least once every couple weeks.Before you get flamed--
IMO the people that ask this question inherently cannot have this request- let me explain.
There will be those that would say what you want is impossible, or a catch-22. I believe what they mean, is that if you have to ask, then you do not have the capability to pull it off.
The kits that are pricy, are not pricy because they use over-kill top of the top shelf parts, but have had the foresight and experience put into them that they work darn well. They are application and time tested.
To do it cheaply- it is somewhat possible. But there are two types- those who pull it off because they have the knowledge, and therefore do not even have to ask where such a kit is, or how to build one. Then there are those who ask, get pissed when people give them good honest advice that is not what they want to hear, and then for the next year we follow their build thread of epic fail as almost every part they buy fails, performs badly or simply won't do the job and they make constant mistakes be it wiring, bad sensor placement, bad component placement etc etc. And then they end up paying just as much over this period of time to make it work as it would have costed to do it right the first time, and/or the car gets put up for sale.
So one is left with two options. 1) pay to play 2) buy some books, do a lot of studying on the subject and become capable of doing it yourself- and in the process learn why those who can, do not roll out the red carpet for those who can't or 3) Jump into it and 'fall down the stairs' into pain so to speak.
Don't get me wrong, there will be those who said they bought "X" cheep kit and everything is great, but take everything with a grain of salt-- they may have a lot of ability, lots of little odds and ends in their garage that for those who don't, it adds up- they often have a mechanic friend or family member, can weld, have awesome fabbing friends, friends in the industry etc, and for all we know they got a great kick-back when buying the kit/parts and they are simply talking it up for that reason. Anyhow, do enough searching around here and I doubt you can refute these points, but rather totally agree with them. If you have the luxury of learning the "hard way", then I say go for it-- its great to learn, and your better off in the end gaining all that knowledge than not at all.