Look, I'm not saying you will get as much from Gazelle as selling yourself. Obviously Gazelle has to pay for shipping and they get it ready to sell, then of course they want to make a profit.
It does seem to vary a lot more with more custom configurations like yours where for example the SSD is not taken into account in the Gazelle estimate.
It seems to be closer with more standard configurations. Here is a comparison I did in another thread in January.
For me, in my example, it is easily worth the $182 not to mess around with it. If it does not work out as favorably in your case, it may not be worth it for you.
I'm showing $665 on Gazelle for your iMac, so maybe you entered something incorrectly.
Yeah, I started with my Serial # which I hoped would catch the SSD upgrade, since there wasn't any way to enter it manually. I also didn't select the top condition option since, even though I don't see any issues, I am sure they would find something with a magnifying glass such as scuffs under the stand.
I was familiar with other "SellYourMac" like places, but was unfamiliar with Gazelle, so I thought I would give it a try. I guess I was underwhelmed. I realize that they have to make a profit and I was OK with that. However they seemed to be quite low in their offering and I wondered if there was any way to more precisely detail what the system had (such as the expensive SSD upgrade).