Bristlebane: Spiderling silk sells for at least 5pp, usually 10 for spiderling silks (at 5pp many buy to resell). Spider silks run from 5pp to 9pp. Some sell both of these for more, but if you want fast sales, you have to look in bazaar and be competitive.
If you want to use auction in PoK or someplace, and sell fast you should try for 60-100pp for a stack of 20 (sell stacks not singles, that is just annoying if you are spamming say the sale of 3 silks). With prices up everywhere, I would never sell less than 60 a stack (that is such a good price I would stop whatever I was doing, to run meet you).