On average, how much does it cost to make a gaming computer?

Well, It REALLY depends on the spec. You can build a gaming computer as low as US$700 (Computer only, excluding OS and Monitor), IF you choose the right spec.

take this spec, for example :

AMD phenom II X4 840

Biostar TA880GB motherboard

4 GBs of DDR3 Corsair RAM (2*2 GB)

ATI Radeon HD5770 GPU

500 GB western digital HDD

Add them up, (including case, DVD Drive, PSU, Mouse and Keyboard) the spec above costs about US$680 (US$800 with windows 7 home premium). And with that processor (AMD phenom II X4) combined with HD5770, You'll be able to play recent games, even on high settings and 1080p resolution!

So...on average, it;s around US$700 to 1500. depends on the spec.

About $1,000. A typical build might be:

Motherboard: $110

CPU: $180

Video card: $220

Memory: $70

Hard drive: $80

Monitor: $160

Keyboard: $15

Mouse: $25

Case: $35

Power Supply: $65

Speakers: $15

Obviously, you can spend a lot more or a lot less.

In total costs, a good midrange Gaming PC goes AROUND $1,000.

You can build them however you want, but recommended builds are around 1k.

Theres some good stuff here

http://www.cyberpowerpc.com/

Or try.

www.newegg.com

Sometimes you can find a full build on one of those websites on sale for a good price.

Make sure you research research research before you buy.

Custom parts. $750

$750 build I did ...

http://www.youtube.com/watch?v=OXC6i98-oxo

If you want save money go with http://affordablegaming.biz/

They have plenty of great options for any budget.