what is a good price for 180 models

It really depends on several factors:

What are they...cars, armor, a/c, etc.
What are the scales...various, all about the same, etc.
Who are the manufacturers...are they all Revell or are there Tamiya, Hasagawa, etc.

I know when the local big collector of model kits looks at buying a collection, he usually groups the kits into three categories:

Small scale military and most autos are $10.00 each
Medium scale military and some special subjects are $20.00 each
Large scale military and big ships are $30.00 each
Then any special kits are individually valued

Bear in mind that he is buying to resell the kits...not to build them himself.

The price you offer will really depend on 1) How badly you want the kits and 2) How badly the seller wants to get rid of them. If they are all decent 1/24 to 1/25 auto kits, you're probably looking at the $1,300.00 to $1,800.00 range.

My advice...make a low-sided (but fair) offer and see what the seller says.

Enjoy your modeling...

I'd say an arm and a leg. It really depends on what the kits are and how much you want them.

I got 68 kits for $100.New ones mostly,like Trumpeter Bonnevilles,Revell cars,some AMT kits,and some high end military kits (1/24 Hobbycraft WWII planes,Tamiya F-4 Phantom...BIG box,and a couple of Tamiya Tank Haulers,etc.,etc.,etc.)The guy needed money FAST,so I got the kits and came away happy.I'll probably sell mine to support my modeling.I don't do military kits,but cars,oh yes.I've already broke into a couple of cars for parts.Some are too nice to use just for parts.There only worth what someone will pay for them.