Aww I did this a few years ago! It was so much fun! I think it was around $18 for the pearl (probably more now). No reservation was required. You just walk up and pay. I think I had to wait a bit because it was so crowded though. Once you select an oyster, the CMs do this super cute little drum ceremony and size the pearl. I had it set in a necklace, but i cannot for the life of me remember what it cost. I think the jewelry prices are pretty inflated though. Sidenote - I really really wanted the Cinderella carriage necklace, but it only fits pearls on the smaller side and mine ended up being too big.