$3000
for two 55 gallon drums, a few pipe fittings, 4 filters, a pump and a fuel nozzle
You could build it yourself for $200 - $500 depending how fancy you want to get with the fueling station and the type filters you use.
All this thing does is filter used oil so you can mix it with diesel fuel and dump it straight into your tank.
IMHO it would be more efficient and cost effective to legs from a pair of old jeans to make a sock filter to get the big stuff out and then filter through a sock filter which costs about $5 before even puting it in the first tank.
Dewatering can be accomplished with heating it to 100C (212F) to boil the water off while stiring it slowly. Then run it through the filtered and dewatered waste oil through a good filter separator before blending it and pumping it into your truck.
My $.02
