I think you've summed it up pretty well, jeeps are a case in point, we all huff and puff at the cost of them but if you are doing a proper job and restoring to factory spec the margin not including time is around the £2k mark on a £14K finished and advertised MB/GPW, I'm assuming here you do all your own work with the exception of engine machining.
25 odd years ago when when I used to restore complete vehicles for customers I vividly remember a telephone conversation with a jeep parts supplier (now no longer trading) after a reeling off a long list of parts needed for a restoration the guy said to me, 'How long did that just take you to read that lot out and how long will it take me to box it it up and send it to you? (The answer was about 10 to 15 minutes in total) he went to ask me then 'How long is it going to take you to bolt it all on and wire it up and spray it and mark it' ?.
The moral to this little story is that even today with the relative high price of jeeps there is still no margin to be had restoring to sell........it's far better selling a box of bits or if you can get them at the right price as projects in from the states. I think this is a general truth with the exception of armour, anything German, and a very few rare allied wheeled vehicles however finding a market for these can be difficult and exclusive.
Pete