What are "postals"? I've never heard the word as a plural.
A $10k minimum offer on the .COM doesn't mean that it's worth $10k. But it does mean that you have a very high ceiling on pricing yours.
In my view, Postals.com would be lucky to get more than $5k (unless there's a meaning I'm missing).
Right now I've seen some disappointing sale prices for single-word .NETs in an auction setting. For instance, Programmable.net (which I sold) went for between $400 and $500. Honestly, I think it's quite a bit better than Postals.net because it's a real word people are familiar with and relates to multiple, high-value industries.
So if you're looking for a quick sale of Postals.net, you'll probably need to ask low $xxx at most. And it might not get any offers above $100.
Of course, it's always possible to do better than average. Maybe there's a meaning I'm not aware of. And this is a pretty bad time to be selling domains wholesale, since domainers are spending most of their money gambling on new extensions rather than buying from one another.