If you plan on keeping your present boat for a long time go ahead and buy them ,but only if there is nothing wrong with them....... Those drives are not made any more and may become hard to find down the road even if you only use them for parts..You can buy replacements for them from another maker but are very high dollars.
i just sold 3 trs drives for 1500 ea, and 2 transom assemblies for 750 ea. i was told that was too cheap by some, but i didn't want them forever. a bird in the hand...
a few years ago I spent ~$750 for just the drive itself, no gimbal, no transom assy/trans.
I was rough on that boat, and should have just bought a few B/W trans as well, I beat those up pretty bad...