When I've wanted to sell a bass fast, then yes--I've posted an aggressive price. But remember that not every bass in the classifieds is a "need to sell fast" item.
Usually I don't need to sell fast. So rather than taking a bath on something, I am willing to wait out the right buyer. If my needs change I can lower the price later. But in many cases I'm content to let the bass sit until the right buyer comes along.
Also, for an unusual bass I have no problem letting people know up front that the bass is worth more to me than what many may consider "market price." This saves everyone time--I don't have to deal with offers below what I'd consider, and buyers only willing to pay "market price" don't waste their time wheeling/dealing with me. In these cases, I'm waiting for a collector or someone with an irresistible jones for the bass I am selling. People pay over "market price" all the time

. You just need to be patient.
I have bought basses at above market value, so I don't agree with your contentiion that "it's all about price." Non-commodity markets don't work that way, so basses that are uncommon/out of production can sometimes fetch prices above "market." For instance, I found a bass recently that's been on my GAS list for years, but doesn't pop up very often (and when it has, I've had other priorities). This time I had plenty of cash, nothing else I needed/wanted more, so I bid well above market on ebay to make sure that bass was MINE. The money was worth less to me than the assurance that I'd get what I wanted. In your book, apparently I'm an idiot with more money than sense. In my book, I'm smart enough to earn enough money to make sure I get what I want, when I want it