I agree too with everything that Chris is saying.
I was going to comment myself that those parts seemed reasonably priced to me. OK the bike market is on it's ar$e BUT rare & decent parts are definitely, NOT as I am proving parting out a couple of my own projects.
If you are restoring something like the early CB750K0/Sandcast or rare bikes like the CB92 Benly, then I am afraid you still need deep pockets, particularly if you want to use genuine Honda NOS parts like the HM300 pipes, which were discontinued by Honda many years ago ... or just search around and find a bike that has been restored and someone has ploughed lots of money into. The plastic CB750 instruments are rare but excellent repro covers and lenses, faces etc are available ... but there again you need a decent functioning mechanism to start with, which is going to cost you.
Early original CB750 exhausts never had stampings ...like many other Hondas of that period ... for example the CB250K0 exhausts were never stamped ... that's why Yamiya 750 repro pipes for the CB750K0 are described as 'No.No.' pipes . TBH anyone who has actually restored one of these bikes knows that fact.