The reliability of the system depends on the quality of components, your skill in installing them and how hard you beat the crap out of it...
I have a Brushless Hyper 7. This is what I have in it:
Medusa 2000kv 60mm motor - $115
Mamba Max controller - $135
SportBEC - $30
MX-3FHSS radio - $150
JR servo - $35
Zippy 4S Lipo - $111
Battery tray - $20
RC-monster motor mount - $50
$646 Total plus shipping and misc parts. I have a custom motor mount made out of 1/4inch aluminum and I already had the servo and radio.
My buggy has been running very well and I'm extremely happy with it. I highly suggest you look at this thread and not try to short cut the learning process by just taking a couple peoples suggestions:
HERE IS THE LINK
Electric 1/8th Scale conversion kits.
MBX5T, 2250kv, MMP, 4S
SC8e, 2050kv, MMP, 4S
RC8Be, 2050kv, MMP, 4S
Emaxx, 1900kv, Trackstar, 4S