Yeah, you would think that an incomplete or damaged bike wouldn't be worth much, but the truth is any stolen bike isn't worth much to the person who steals it. The vast majority of stolen bikes get sold on at a pittance - £40 guess is about right - regardless of quality / completeness to someone else who then fixes / resprays / swaps parts and then sells them on via
ebay / gumtree as "legit" for around five times the price they paid for it. These people have spare (also stolen) wheels coming out of their ears. It's an organised crime.
I already explained this:
You would think that, but you'd be very wrong. The scrottes doing the grunt work sell the bikes on at a pittance to someone else who then fixes them up / resprays / swaps parts and then sells them. These people have tonnes of spare parts lying around.
If you don't believe that, how would you explain all the wheels you see d-locked to railings, where the bike's been pinched leaving the wheel still attached?
Bikes are also stolen to order, in a similar fashion and the scrottes are willing to change a few parts here and there when the 'customer' is paying a premium.
Please don't use the Sheldon method to lock your bike - you are asking for trouble. Any locking method that can be defeated with a hack saw in less than a minute is an epic fail.
On a side note, £40 for eighteen seconds work seems like a good deal to me.