I'd say somewhere in the neighborhood of 10-12K.
GG
The prices on these are highly variable - just like any car or truck you would buy here that's not a JDM.
Without knowing what has been done to the truck, and exactly what options and features it has, it's impossible to come up with a price.
Cable locked BJ74s are all but impossible to find now in Japan - I know about it, as I've been actively looking for them. Also, the costs on the Japanese side of things has been going up. The Yen is up compared to the Canuck buck, and shipping prices have gone up. Compliance is costing more, not that a BJ74 needs all that much, but it is another thing to factor in.
For a clean and locked BJ74, in either 5 speed or automatic, the prices on this side of things will range from a very low price of perhaps $13K to upwards of $18 or $20K for a high auction grade truck with most of the common bells and whistles.
The higher prices also will reflect the maintenance package that any given importer has invested into the vehicle - and don't underestimate the value of this: I work on many JDMs at my shop, and many owners are sucked in by low prices on vehicles that have only -just- been complianced. They find out later that they need to invest $100s and even $1000s in bringing the maintenance up to scratch - and the seller has no responsibility to the owner at this point.
If you're looking for a truck that has lockers from the factory - and it's a clean one - get it! They are pretty uncommon, and they will hold their value well if you keep the rust gremlins at bay.
There are a few cheaper, non-locked BJ74s around - I think they generally represent good value, and you can add ARBs for a reasonable price.
In summary, I would have to say that you should pay what you feel is a comfortable price for any given truck. If you're not mechanically minded, get it checked out by an independent shop (independent from the seller or dealer), and be very aware that many (most all) of the JDMs that I have seen over the last couple of years have had cooling system issues, among other things (rusted brake rotors, seized calipers, dry knuckles etc).
Hope this helps...
~John