I have bought most of my astro gear second hand on IIS and my experiences have been almost entirely positive. I have never made an offer and have always paid marked price. If I can't afford it then I can't afford it and I won't try low-balling; I don't want to be that sort of person. I also have (or had) a shopping list to which I try to stick. [There have been a couple of impulsive ep purchases but nothing much.] So I am willing to sit and wait until the desired item comes up for sale and, in the case of scopes and mounts, within reasonable driving distance. As part of that process I used to read just about every classified add so I would know the right item at a reasonable price when I saw it. I still view many adds just out of interest.
Looking back, I wonder if I ever ignored an add because I felt the item was overpriced? (as opposed to the price being reasonable but out of my range) It may have happened but I can't recall it - but then I probably wouldn't.
These days I have all the scopes and eps I need ... OK just one or two more eps
and so I'm not in the market. I see nice gear on the classifieds but I can't buy because the cupboard is already full. I suspect a great number of IIS members are in the same situation. I wonder whether much of the difficulty in shifting astro gear is due to market saturation?