It doesn't look like a cheap-o web page, and it might not be a bad idea to take a "hit" on your selling price just to get rid of everything in one go and before you change your mind.

used instrument buyer

But this makes me a little uneasy...

"simply pack your equipment, ship it to us FREE, and we'll promptly mail you a payment."

I can see me standing there in my room where the music equipment use to be and nothing but moth balls in my pocket where the money should be!