How best to negotiate reasonable prices?

[Asomer]

I came came across a C/L seller in Indianapolis(I'm in Texas, so shipping costs would come into play,) the other day selling the 2 of the exact same RH sofas I've been looking at & a RH coffee table: everything is 2yrs old. The sofas have the same down cushion option I'm wanting & dimensions, just not the slipcover fabric or color I'd prefer(yes, they're linen slipcovered sofas, NOT leather!) A new RH slipcover runs @ $800-$1,000 depending on fabric choice, size, etc...LOL, keep all of this in mind for when I tell you how much they've been asking for each sofa:

They claim they paid $3,595 each, not inc shipping for the sofas 2yrs ago(sounds bout right.) They def don't look brand-new in the measly 2 front facing pics they've posted. Yet, they don't look beat up either, just normal...yet, they're asking $3,500 for each sofa?!?!

Lol, for that price I could buy it brand-new in my desired fabric & color!! They said they're willing to negotiate as the listing's been up for over a month now & NOTHING in the listing has sold.

My question is, & this applies to any & all used furniture items being sold on eBay & Craigslist: how do you go about asking for less & negotiating a reasonable & fair price without insulting them & souring the deal? Especially when they're asking just shy of what they paid retail for? So many ppl on those sites think they can recoup their full investment regardless of however long ago it was on used furniture! Without sounding overly judgy(LOL,) they look like uninformed idiots who have absolutely no clue what they're doing...and, they wonder why a month in & nobody's buying what they're listing!

I got the impression they were insulted when I offered $2,000+ less than what they're asking for(I offered $1,200 initially, then $1,500.) Those sofas aren't worth $3,500 new & they most definitely aren't worth $3,500 2yrs old!!

Any tips & techniques or advice would be great for future reference & perhaps this could become a sticky to help others coming across similar situations?

Andrea