As usual, I think Chaad is right. Here is a company that sells corks if you're interested:
Their top end cork is around fifty cents if you buy 10,000 or more. But it's a 1 3/4 inch cork, which is kind of the base level for most people who are paying for a premium wine. Don't you want to see a 2 inch cork come out of your bottle? Somehow that seems more serious. And those are usually the best material too.
Not only that, those longer corks will often have gone through extensive cleaning and testing. There are a lot of people selling cork, and this is an ironic instance where the small, artisinal cork maker/dealer is what the small, artisinal winemaker should avoid. In fact, the winemaker should deal with the large industrial corkmakers who can vouch for the cleaning and the provenance of their corks, from the tree to the bottle.
And then the winery may do additional testing. Vega Sicilia for example, sends their corks to a facility in Bordeaux for examination. All that costs money. And it's unnecessary in the case of rubber corks. Then, if you're a smaller, boutique winery, you don't get the volume discounts either.
Of course, at the end of the day, I'd rather that the winery spent a buck or more for the cork and used a cheap bottle, rather than have some high-shoulder bottle and a cheaper cork.