Try Galls.com and shop their clearance section. The NIJ testing standard for armor recently changed, so armor certified to the old standard can sometimes be found on clearance. (Testing was amped up and velocity standards increased.)
I've used armor regularly since 1998. I've always purchased IIIA armor. Originally this was the hot ticket back when entry teams had MP5s, since IIIA did a good job stopping 9mm rounds at SMG velocities. It also reduced blunt trauma. The 5.7 FN, imports of large numbers of Tokes and Czech Model 52 pistols, and the .357 Sig have also contributed to the IIIA level becoming more or less standard.
You don't mention if you're doing domestic work or not. If you need non concealable armor with or without rifle plates, the Izzy Marom Dolphin rigs are about the cheapest thing out there that I'd take a chance on.
Usually the more you pay, the better the armor you get in terms of being light and comfy. My mid priced Second Chance IIIA (regular old Kevlar) that I got when I got married is hotter and stiffer than my old circa 98 Point Blank Hi Lite IIIA, but then it cost half as much.
Do you need armor certified to mil. blast standards? If those, that tends to cost more. A first line set of tac armor, ESAPI multi hit plates, and a nice carrier can be 3 to 5 grand.
For an acceptable concealable, eh... 400 to 1200.
For a basic Izzy rig, maybe 700 to 800.
I paired down my armor for a planned upgrade that didn't happen. I still have a Second Chance concealable and then I have my Izzy tac armor with Level IV plates.