it means plus one. Like the poster above said 175k. Plus 1 means 176k. When you see the next +1, it'll be 177k and so on. This is how cars are sold at higher prices on Pakwheels, everyone adds +1.
About the current market value of this car, I can tell you that a totally problemless car may be sold upto 250,000. A car with issues etc - you've been rightly told 175-200k.
but the resale is slow.