If you are looking for the shadiest dealers on the internet, look no further than people who sell used domains.
You are looking for a car - not just any car - but a specific brand, make and year. You have an idea that has been gleaned through nothing more than just pure living of what the vehicle should cost. To help you confirm your estimate you have tools at your disposal to help you make a better informed decision. Some of them could be the Kelly Blue Book - eBay - or even Craigslist for comparable vehicles and their current price.
You find several 2004 Ford Expeditions with four wheel drive, 100,000 miles and decent shape all in the area of $4 - 6,000 available for sale. The local car lot has one that has caught your eye and you head over there to negotiate a price. Imagine if you arrive there and the salesperson blabs out "If you are looking for the only Ford Expedition in the world - this is it! I can arrange a test drive and then financing for $40,000 today - but you gotta hurry."
More than likely you would roll on the floor laughing and high tail it out of there never to return.
What if the dealer said "I can get you this car today for only $2,000 out the door but you will have to pay a relicensing fee to us each year of $1,000 a year"?
In both cases you would probably just bail and be done with it.
Now comes the guy who resells used domains. Unlike a used cars, domains are much trickier.
To begin with, there is no "Blue Book". There is no eBay for competitive bids. Craigslist is of no use. The only thing you have to go on is this guys (or ladys) word and nothing else.
It will always start the same. "This is an incredible deal on a HIGHLY sought after search term. It won't last long. You have to get it immediately before someone else does." Even GoDaddy uses this technique in their funneling channel. "Grab this domain before it gets away"
If you try to use online tools to get a better idea of value, don't count on a lot. There is one called Estibot that is wildly all over the place. It literally runs a quick tally on the popularity of words and then pulls a number out of its logicalyzer and spits it out. Let's make it a bit easier for you - if Estibot gives you any number of $1,000 or more - you can almost bet it is a winner. (Easy enough?)
GoDaddy also has a valuation tool that is wildly all over the place.
Used Domain Salespeople realize this and count on it. In fact, they relish the fact that by and large the populace is blind and ignorant to what domains are worth. So, they work up obscene quotes and then lay in wait for the next sucker to pass by. If you have the misfortune of dealing with someone from the dot com dealers connection - you are all but lost. The URL is untouchable, it is invaluable, it is impossible to replicate and it can be yours for the obscenely overpriced amount of _______.....
If you pass, they won't let it rest. In fact, just like a high pressure timeshare salesman they will come back to you with a counter after considering your good nature - because they really really want y-o-u to have it and it would mean a lot to them if you did get it. Pretty soon, it will continue going to a point where the poor guy won't even be able to afford a meal if he goes any lower.
God help you if he/she really does have another interested party in the same URL as you. Then it will be entirely different. Upward spiraling prices out of control until one of you pops.
Save yourself the grief. Find a suitable generic top level domain at an affordable price and build your dream.
You will thank yourself, your pocketbook with thank you, and the poor soul you were going to bid against for the dot com will thank you.
Only the used domain salesman won't thank you.