I'm no expert in pricing 45's, however I do have experience as I just purchased mine about three months ago. The below numbers refer to the pick ups as I have no idea about the LV's - yet. . . .
After many years of looking at 45's online (since I have never seen one in person since the '80s), the prices range from the low $1,000's to some ridiculous numbers - I've seen one on ebay with a starting price of $ 75,000. It didn't sell. No bidders. Go figure.
I found the majority of them fall in the range of $ 6,000 - $ 12,000. The specs will range wildly from bone stock to V8 conversions. The vast majority of them will require some work, usually body. Occasionally there will be the odd gem out there where the work has been done already for this price range. I remember an orange 45 pick up being sold that appeared to be very sound, albeit it did have a flatbed in lieu of a box.
There have been a number of Right Hand Drive units sold in recent years and it appears that many that come from Australia and New Zealand are in good shape while the ones the come from Central America generally require a lot of work. There are certainly exceptions to this.
If you are hunting for one, you have to ask yourself:
1) Do I mind RHD vehicles
2) Do I want stock or modified
3) How much work do I want to do on it
And the most important part - how much do I want to spend. IMO, the key is to start with a solid frame and decent body. The engine, tranny and everything else is certainly easier to obtain.
I bought mine - a '67 LWB from SoCal. It boasts a nearly new 454 with a bunch of Edelbrock components mated to a 4 speed tranny. The majority of the body is very solid, however I will have some work to do on the hard top. I picked it up for slightly more than the range I quoted above. I justified it because it had a new engine, decent body, solid frame and was the last year they were imported into the US.
The one I really liked was a '65 SWB V8 pick up (I think it was red) from SoCal and it looked really really nice. It was on ebay and I think the Buy It Now was somewhere around $ 50,000. The auction made it up to $ 25,000ish and it didn't hit reserve.
There was a refreshed and fairly original 60's vintage that went for about $25k on ebay a month or so ago. FJ45LWB. Beautiful truck but the work hadn't been a frame off and some of the choices the guy made in colors and use of bedliner wouldn't make everybody's short list.
I could definitely put that truck in the "reasonably priced" category though for it's condition.