"Market value"is set by the -need- for the truck and it's attachments (mast height, etc..) at least as much as by the condition of the unit.
There are plenty of well cared for and excellent condition but very special designed forklifts that have almost no resale value, since no one else could use them for anything.
You -could- just go to the sales side of forkliftaction, and find a few 5 year old (maybe just off lease) 3 wheel electrics to get an idea of what they will be worth when 5 years old.
I am willing to bet a few sales types are thinking the price you are paying for a 3 wheel electric (35k) is a bit on the "nice for the sales departments numbers this month" side, if you know what I mean... It must come "really complete"...