Let's face it, negotiation is still be maker or breaker of most domain sales. I have to admit that there are so many folks who are good at negotiating, but you didn't get there from the start.
You do have an edge when buyer reach out to you, but in this case, lets look at the outbound sales.
So how did you improve your domaining negotiation skill that has really helped your sales? I mean the factor that has helped you in winning sales in 4 figures when you reach out to end users.
What give you the confidence to ask for 4 figures?
One of the reasons the rich get richer is because they are less desperate. If you are desperate for money you cannot possibly negotiate correctly, you must allow an independent party to negotiate on your behalf, a party that is not desperate for funds that has a vested interest in getting the highest price.
I bet between all domainers on this forum tens of millions of dollars were lost because bad negotiating skills.
Outbound marketing becomes null and void the moment they reply. Now they are just another company who have a liking to your name and you should treat them as such, set aside the fact you emailed them.
You need confidence to ask for 4 figures? Just look at some of the names that sold in the past week for 4 figures and it will give you all the confidence you need. As to how to justify it to the buyer, well in most cases you don't have to. One of the biggest mistakes domainers make is not realizing that while a 5500 exact match monthly might seem great for us, for some know nothing domain buyer that might be a huge turnoff, they are dreaming of millions of hits and you tell them reality.
Share with them the sales prices other names sold for and dont tell who what when sold it or they will go there and find another name they like.
Use the anchor technique, demand a huge price for the name and work your way down. The pros in this business do that and they follow up over time with discount offers etc.
Do what works, once you make money try your own methods.