I agree that you could possibly get more than what sp would offer you
I should have qualified that with saying that I have very limited experience selling pipes online. I've sold just a few. I don't like the process either.
The latest and only pipe I had "appraised" was fairly expensive. The vendor in question hadn't even seen it, but knew what it was because they sold it to me. Assuming it was in as pristine condition as I said it was, this (I'll keep it private) was the maximum amount offered.
I more than doubled that in a private sale. Which makes a bit of sense. They needed their cut, so I sort of assumed it was about 40-60% less than what they expected (and what I wanted before even contacting them).
I listed it as a "Buy it now" auction. I think that is the key, which I didn't mention. A straight up auction and you may get screwed, due to lower traffic than the major resellers. A "buy it now" auction is free and you can go on forever, if you have patience.
I had low ball offers, etc., but I knew what I would part with it for and left it up until someone eventually bought it.
It took about 3 weeks or so and e-bay got their 5 or 10% cut (I can't remember). I'm only suggesting that if you have time and an idea of what it is worth, I'd first put it up at that price before contacting a reseller,
which absolutely have their value in certain conditions.
But that's just me. I can be stingy when it comes to saving a buck... or several hundred of them.