A really great answer by
@iAchilles !
I would have had a figure in mind before the first contact, but look only forward! It is very positive that you got a reply at all!
I would look on Afternic, Sedo and Undeveloped to find the most similar names you can to yours, and see what they are asking. Now a lot of people ask crazy high, so don't think a super high means you will get that.
Next I would go to Namebio, and try everything possible to find comparators. For example, if it is a two word name, try sale that lead with the first, and then a new search that end with the second, etc. I would note the few that seem most comparable and use that as guidance in setting your price, and also to justify the price.
Next I would go to GoDaddy GoValue and see what they say it is worth. Now that may not be even ballpark right, but if higher than you plan to ask is good bargaining information. Don't just look at the price, look at their comparators. I find they often have some not in Namebio.
Next I would try the name in Estibot (2 evaluations per day are free). As well as a figure, they will give you lots of data re Google searches and CPC by advertisers that may be helpful to know.
Now you are ready to make a response. I would decide what you think is a fair price that you would be happy with, but also justifiable on data, and add maybe 30% to that. I would give them that price, but with some wording showing that you are open to negotiation.
A super key question is whether the name is potentially useful to others than this company. If not, then I would really be flexible and try to seal the deal. If others in industry might use it, it might make them more keen to not let the opportunity pass.
Best of luck,
@Coinking !