Having just moved from SF to NY, I was looking through the recent Wine Spectator survey to find a good restaurant on the UWS with a reasonable corkage fee. It turns out that many, if not most, of the corkage fees listed are incorrect (listed as significantly lower than they actually are).
For example, Nice Matin is listed at $10 in Wine Spectator's survey but when I called to confirm it they said it's actually $25, enough for an about-face since it doesn't seem like a particularly good restaurant in any other way.
Les Routiers is listed at $15 but they told me the actual corkage fee ("upped about six months ago") is $20.
For the inferior glassware these kinds of restaurants provide, these fees are unreasonable.
If you're counting on Wine Spectator, make sure to double-check their data because they seem to be very unreliable in this regard (and they're based in Manhattan!). On a side note, it's disappointing how many Manhattan restaurants neither allow BYOB nor maintain competent wine lists (esp. representing California and Italy).