Great topic... and one that is very much a moving target-- cork processes and process controls have improved considerably over the last 5-years, or so. But, the performance of synthetic closures has also improved considerably.
Regarding the size of corks:
A 49mm cork is generally regarded as a 2"-cork. Like lumber dimensions, they're not exactly 2".
We buy our corks from Amorim (http://www.amorimcork.com/default_alternate.html) , they are the highest domestic grade available, 2" size, and they cost $0.84 each. Their performance has been very good. They offer a higher grade from Europe, special order, called "Fina". I believe those are somewhere between $1.10 and $1.25 ea.
Depending on the producer, the price may be just cosmetic (the absence and size / type of of imperfections), or it may have to do with both appearance and their testing performance.
On the other hand, I've increasingly become enamoured with Noma Corks:
These are great closures, and by most accounts, they perform extremely well. I like the way they go in, and come out. I also like the fact that storing wine upside down, or on its side, is no longer essential. I like the fact that they are consistent. I also like the fact that they are considerably less expensive; however, I don't really consider that a major decision point for a wine like Le Cadeau. The fact is, my current view is that all things considered, they are a better closure.
We've made the move on some of our less costly wines, but based on what I'm seeing in terms of performance, it's very tempting to make the move across the board.
Still... there are those nagging issues of "perception" and "romance"...