A CB550 for that price should look like new and need only routine maintenance for the next two years.
The trick is to determine if it is truly in that condition.
It should have 10K miles or less.
New tires
Brake fluid should be new. Front brake works well and doesn't drag/squeal.
No leaks (though with regular use, it WILL start weeping at the cylinderhead, provided it still has the original o rings in the oil passageway)
New battery
New fork oil, perhaps even new fork seals.
NO dents, bents, or scratches.
Seat soft and supple.
No rust inside the tank.
The fuse clips should be bright and shiny. This is a general indicator of the electrical connection condition throughout the bike. These can all oxidize over time and give poor charging, intermittents, melted fuses, etc. It's about a day's work to clean and restore all these connections and return them to reliable status. For $2750, this should already have been done, or the bike has been stored and kept in such a way that the connections are as new.
The chain should be new. Or, if original, not a spec of rust on it.
Starts quickly with choke, idles smoothly at 1000-1100 RPM, after brief warm up, (time depends on outside temperature.)
The NOS exhaust is worth $700-$900. If you like that exhaust (I do), just tack that on to what you would pay for the bike.
Most of us here work on these bikes. We'll put a couple thousand in parts into a bike we have or have gotten cheap. But, we won't pay someone else to do the work for us, or for storing and maintaining a fine example for many years for us to enjoy after purchase.
If the bike has more than 10K miles and has been restored, then it is prudent to check for rocker shaft cam cover wear.
On the inside of my 1974 CB550K owner's manual is the notation:
Purchased 3-30-74 out the door price $1880.49 which includes crash bar,tax & license.
What is a 1974 dollar worth today?
Cheers,