Here's my assessment, for what it's worth:
I see several (at least 4) PC XT era monitors. I see several (at least three) newer PS/2 generation monitors. I see several (at least 2) third-party monitors. I see a PC or PC/XT, and a PS/2 model. I see an Apple //gs power supply, a Apple 5.25" Drive, and what is possibly a Rana full height disk drive (for Apple or Atari). I see a lot of cables. I see a cool red dial phone. I see an old heater. I see boxes. I see a lot of junk. I see a somewhat dilapidated trailer that is way bigger and is supposedly holding more stuff than the photos do justice.
There just isn't enough information. You could try to extrapolate what might be there from the clues above (lots of PC stuff. some Apple stuff, lots of old junk) or you could try to get more information. To that end, I contacted the seller and asked for more photos. He said he would provide some tomorrow, but in the meantime he offered up that he sold a "bunch of pc xt at ps11 Keyboards". I'm not interested myself but will pass along photos if he actually sends some. Someone really needs to go out there and get inside that trailer and inspect it from one end to the other to see what's there.
Assuming the contents inside are worth it, I'd offer what it was worth minus 50% up to $980 for the contents. In other words, offer half what it's worth up to his $980 flat offer, or less, maybe $900. The clean-up work and disposal costs will not be insignificant. If agreed, show up with a team of 6 people and two big U-Hauls, one for the keepers and one for the junk. Start tearing through the trailer and make a quick decision as to whether to keep or junk, and sort out the junk into donatable items and landfill. Drop off the donatable items at a Goodwill or whatnot, take the rest to landfill, and then divvy up the loot. It would take a day but you'd get all the heavy sorting out of the way. Sell off enough to re-coup your investment and revel in the glory of having accomplished a Big Score.
My best assessment: it's probably filled with a lot of PC crap that either might or might not be worth $980. A couple or three complete IBM PC systems might get you to that amount, and assuming the rest of that trailer isn't just filled with garbage and you're into PC stuff then it is at least worth a gander. But to pay $980 for it sight unseen would be foolish in my estimation.
I agree with the prior opinions on the trailer, it is junk and a liability. Leave it be.
Sellam