Yeah Cheapest and body armor go together like "Cheapest Deep Sea SCUBA Gear" or "Cheapest Brain Surgeon' ....buy what you can afford; more $ does not always mean better quality but as a general rule it does.
I hear good things about this place:
http://www.bulletproofme.com/
They seem willing to do custom work too; which is great for us tall guys. @ 6'7" tall the couple of times I tried on my friends vests I felt like too much was left exposed and I mine as well not be wearing it for what it cost me in comfort and mobility.