Rest assured, Melling isn't going to let a retailer sell their seconds as new and perfect.

Here's why:
Melling is an industrial giant but not a retailer. So Melling depends on its retail dealers to sell product. Ever notice that you can buy parts from discounters for less money than going directly to the source? The same reason exists. If the manufacturer starts undercutting his dealers he won't have dealers any more.
And so it is with factory seconds. Either they are destroyed before leaving the plant, or they are marked as defective and wholesaled out. Anything else just hurts the manufacturer's business.

There are two reasons why one chain will sell for lower price than the others:
1. Like Walmart they jawbone the supplier into giving them a better price.
2. They are willing to live with a lower profit margin.

R.

Years ago I was in the market for a new French horn (kid's in the band). So I scoured the marketplace and found the two or three brands and models that would be sufficient for a teen through adult player. I started looking deeper and discovered a small music store that was dealing in seconds from the maker I favored. These were clearly advertised as seconds. Some had finish flaws and some had a sticky valve or two. They came in factory box and case and had an identifier stamped into the brass near the serial number. There was no guarantee.
Because I was familiar with brass instruments I bought one. $1355 plus shipping. Retail was $3999. After 10 minutes messing with the valves, they were free and the horn worked like any other new one.
In this case the manufacturer moved substandard inventory without harming anyone. They did not lose the material and labor cost, the small music store made a profit, and the retail sales weren't hurt a bit because the people who are buying these horns expect to pay full price, and they wouldn't even consider buying a factory second.