I got my first gaming computer back in 2005. It was a pre-built DigiPro computer with the standard DigiPro case, 256MB of RAM, Geforce 5200FX GPU with 128MB of memory and a 3GHz single-core Intel Pentium 4 CPU. I do not know how much it cost, I was 13 years old and my parents bought the thing for me.
In a way, I'm still using the same computer even though none of the components are the same anymore. I kept on switching up components depending on the need, getting a RAM upgrade here or a new power source there. I only did a major rebuild twice, once in 2008 and once last year. In 2008, I got a new motherboard, CPU, GPU and RAM. The specs were at 2 GB of RAM, Geforce 9600GT with 1GB video memory and a 2.7GHz dualcore AMD Athlon X2. The upgrade cost me slightly more than 200 Eur total.
I got a new GPU in 2011 and then did another major rebuild last summer. I changed the motherboard, RAM and CPU again and this time, I also got a new case (the old one couldn't cope with the amount of heat generated by the newer hardware and the thing would overheat as a result). The GPU cost me 170 Eur, the rest of the upgrade was around 300 Eur.
I'm currently at 8GB RAM, GeForce GTX560 1,5 GB and a 3.2 GHz quad-core Ivy Bridge Intel i5.