Barring any difficulties, it looks like Terraria will make its retail debut on Monday May 16th. So much for 'sometime in June', neh? Hopefully this is not a rushed release but rather a happy coincidence. Lacking any additional information, I would guess that the Steam integration and other backend necessities (legal,, contracts, etc.) have all been concluded a bit faster than initially suspected.
The launch price for Terraria has been stated as 9.99$ USD. However it has also been mentioned, on the Terrarria IRC channel, that this price may go up after a while. As of this blog entry no information is yet known on the pricing for other regions, or what the full price after the initial launch sale will be. It is hoped that a reasonable price will be set for each region that Terraria will be available in.
Looking forward to Monday!