Hammarlund

I'm going to be selling a collection soon and I'm curious if there's any predictability.

Say that there are three coins showing at $200, $1000, and $5000 on the NGC price list:
1) Am I correct to conclude that this is derived from some sort of computerized analysis of recent sales, presumably on Ebay or elsewhere?  Or is that limited to dealer reports, a la the Kelley Blue Book?

2) What is the usual relationship between NGC price and sale price on NGC forums

3) What %age do most dealers tend to pay

4) Is it even worth talking to APMEX or do they simply exit to low-ball foolish people by offering melt value

5) is there a simple and reasonably accurate price site anywhere--even if it requires a paid subscription--which will search and display straightforward information from multiple sites at once, for example listing "ebay 6 month median", "ebay 6 month mean," NGC Price Guide," and other sources all at once?  Bonus points if it will also include some sort of registry or database.

Yes, even as a newbie it is obvious that some sellers (including some on ebay) will deliberately collude to "buy" their own listings at an inflated price in order to drive up the market.

So when I find myself asking "Why did someone just pay over $2,000 for a basic two-coin set of 2013 silver eagles?" the answer is "they didn't; it was the seller."

I have all four: Platinum, gold, silver, copper.  And yup: Those are the ones I mean. Thanks for info.  Odd, isn't it, that there are no serial #s or grading?

Anyway, on to the next question: How does one decide re the worthiness of certification?  For example, I have a 10-coin set of late 1800s and early 1900s liberty $10 gold coins, and 20-21 equivalent $5 gold coins (attached, and including a $20 as well).  In the context of selling it seems a bit odd NOT to certify them, but it's a pretty expensive process to do so.  And that isn't even counting the multiple bulk sleeves of silver dollars--both Morgans and Eisenhowers--which are similarly uncertified.

What resources are people using to make these choices?

I will be selling off a medium coin / metals collection. I can handle the ungraded coins just fine, either by submitting or by selling ungraded, but it includes a number of odd ducks and I'd welcome comments about the best way to approach sales

First, I have a handful of things w/ an NGC cert but no NGC number, specficially a set of "1861 confederate cent Smithsonian "Restrike" 150th Anniversary .999 gold/platinum/Silver/copper Gem Proofs"  I didn't know you could get an NGC sticker without a number...?

Next, I have quite a few non-certified Washington-Mint-type mix-metal or single-metal pieces, e.g. "gold plated 4 ounce silver bars in the shape of a $100 bill.", "giant half-pound silver eagle", and such. 

Any ideas on the best pricing resources to track such stuff?