The market value on 80 series has dropped because they are no longer being bought for export to other countries.
For the past several years they have been high demand vehicles in S America, Africa, even Russia and other E European countries etc, places where if exported through proper channels benefited greatly from the weak dollar or rather strong exchange rates from foreign currency. Mileage didn't matter, a truck with 230k brought the same as a truck with 130k when thay were all just going onto a boat to be exported. This drove the price up on every 80 series sold accross the country for the past several years.
When that market dried up, very few people were left to purchase overbuilt but outdated, under powered, relativly poor front and rear seat room, poor mpg, parts that cost 30% more than other Toyotas 12-18 year old vehicles........Well we are really the only ones that really still desire these vehicles. Granted there are lots of original owners out there who still love the 80 series they bought new and are great ones to scoop up when they eventually decide to move on to the next vehicle thay will keep 15-20 years.
There will NEVER be another vehicle built to the standards that these vehicles were built and designed to meet. Areas where these vehicles were originally designed to reach are becoming more accessible and those countries become more civilized each decade and unfortunately the push is toward more disposable vehicles, not ones with simple in line 6 cylinder engines, locking differentials, solid front axles, and parts designed to last 500,000 miles.
At the current market, I can have 3 or 4 more 80 series for the price of one used late model suv!!!!!!!

I think I am off to search craigs list.