I have never sold any higher end pins but from what I have seen and my personal experience selling under $3000 machines the best way to sell machines is to price them at the lower end of retail value for a quick sale and never look back.
Using Jurassic Park for example (since I have experience with that machine) and calling it a $1800 to $2200 machine. Instead of asking a crazy price like $2800 for it figuring you might get lucky and find someone really looking for one you are better off listing it at $1900 to $2100 and more or less holding fairly firm on price.
Way to often these days I am seeing crazy prices on machines and within a day or two the sellers have already posted 2 or 3 times with "price drop" on their machine. Start with a realistic asking price and machines will sell quickly this time of year.
A couple things to remember - first off - if you sell off all your machines and head down a different path you can always buy machines again if you decide you want machines again. Yes - you might sell at a loss or have to pay more later to replace a machine but if you truly need to head down a different road - long or short term - nothing says you can't replace any machine you are selling later on if you want to.
Second - think it over and don't do anything without giving it a good bit of thought. But once you decide to sell just sell machines as they are. Don't remove parts like shakers trying to milk a few extra dollars on machines. This will just make it harder on you for a longer period of time.
And lastly - selling machines one at a time will net you more money (normally at least 10% more per machine).
Regardless what you decide to do - best of luck to you. Life changes and making changes as life changes is sometimes hard but in the long run all will work out.
As far as best places to sell - that varies from area to area but Pinside, RGP, Mr Pinball and Craig's List are all good places to start. Why pay fees somewhere like eBay when there are so many free places to list machines?
Just my 2 cents on things!