I've got two Brooks B17 saddles that I swap between my bikes.
Both were bought second hand for £35.
One is significantly more used than the other. This more used one is the most comfortable of the two, and the most comfortable saddle I have used. I can ride all day without any discomfort at all. It did take about 200 miles to get it shaped to my bottom, rather than the bottom of the previous owner, but now it is perfect. Unfortunately, I have no idea how many miles the previous owner had used it for.
The newer one is harder and stiffer. It also has much more of a shine to it and is significantly more slippery to ride. I am hoping that the shine will go and it will soften with use.
In short, buying second hand is fine, if you look at several and get the one that best suites your bottom and pocket...
J