I bought my 88 K5 aprox. 3 years ago in southern cali., for $5k. It had not been modified much. 6" lift with blocks in rear, 35" mud tires and aluminum wheels, pearl white paint over red undercoat and clear top coat, alpine stereo, infinity speakers, stock but very good interior, recent rebuild on trans (700r4), no rust at all, silverado package with electric locks and windows, tow package.
I wanted a clean blazer and this one had a good size lift and tires, so it was worth it, especially compared to the other POS's out there that were $2-4K in price.
I spent about $1700 on parts for my stereo and did the work myself, replaced the heater core, did a brake job with new parts that came with the truck, installed a tach., installed a remote start alarm, installed a K&N air filter. The engine had bad valve guides (smokes on start up and uses some oil) and sucks for power, but it runs good and is fun and reliable. It still needs a gear swap or axle upgrade and the tcase likes to slip out of 4wd.
My 79 chevy pickup and 88 K5 are an investment for the use and pleasure I get from them, I do not intend to ever sell them, do I keep them nice and spend the money knowing I won't get it back.