Well, original price was $30, that $9.99 price won't last for long before they get rid of them... Sam's usually has some pretty decent deals for things, especially when they clearance things out... For the qty you are getting I guess you could just chuck them when they are dull, I'm sure they would be fine for wood but I probably wouldn't even bother with metal.
For $10 though it's almost worth it just for the metal box. I wish my sam's had them in stock... Sadly, even living in Bentonville (Home of Walmart/Sam's) the Sam's Club is kind of small and doesn't stock as much as you would expect.
I have a DD750X I bought used for I think $40 and I'm really happy with it. There was a little learning curve but for the most part it sharpens bits very nice and consistently. I also like that I can do masonry bits...
I bought a couple packs of Skill bits at Lowes or HD when they had them clearanced out for $9.99 (I think it was a SKU changeover).