It's an interesting concept: a bloke getting upset or concerned at the price another bloke gets for his bike... The old adage "it's only worth what someone is willing to pay" comes to mind.
The OP's predetermined price range in mind for each set/group/class of bikes is pretty spot on but I ask: what's the big deal if someone asks way above that range for their bike? Good luck to them I say, if they're a motivated seller they'll eventually meet the market - buyers determine what something is worth, not sellers.
What's more frustrating to me is the "what's this worth?" posts - fishing for bites instead of researching the market....
And the most weird: when some guy posts a pic of a handful of cash with the words "I've got $2500 what's out there?" Does that actually work?
I get frustrated by the bullshit that goes with it - including the fishing expeditions, and all the rest.
It's beyond frustrating when you see shit you want, advertised for silly money. You sit and wait for a month until the seller finally wakes up and starts dropping the price - and then sells it for LESS than you were abused for offering a week earlier...
There are bargains to be had if you can put up with the dipshits, but you'll waste a lot of your life dealing with 'gangsta' morons, and sad, lonely losers before you get the occasional bargain.
Time waster/scammer/moron behaviour:
"Offers" (which is totally different to $X, ono).
Price way above the market.
No/minimal details.
Asks for swaps, without ANY hint of what they're looking for.
Shitty photos.
No location.
Dodges direct questions.
No phone number.
General sense of self-importance ("Why should I put up info about the thing I'm selling?" or asking the seller to inbox them, etc).
I have a rule of thumb for items over $100: If there's more than three PMs without a phone call (or a phone number being provided, at least), then they're probably a time waster. Obviously there are exceptions, but its a good start.
Edit: "What's out there?" without any more details is about wanting attention.
A photo of cash is a useful tool among the dumbarses. The photo of the cash 'proves' that they actually have the money, and might be the rare non-time waster...