Butland, who made his England debut at the end of last season and later played for Great Britain at the Olympics, denied Dean Hammond with a spectacular stop down to his right deep in stoppage time to preserve the 2-2 scoreline in the npower Championship class.
The 19-year-old is attracting attention from a host of clubs, and Clark said: "I hope that save puts another £2million on his value!"
A blunder by Brighton goalkeeper Tomasz Kuszczak moments earlier had allowed Birmingham to draw level.
Brighton appeared to be heading for their fourth win in January until Kuszczak fumbled a weak close-range header from Nikola Zigic.
Clark had every sympathy for Kuszczak, saying: "It was great for us but unfortunate for the goalkeeper.
"He played particularly well and then he made that mistake. Outfield players make many mistakes and don't get punished. But a keeper makes one and it usually ends up in the goal.
"That is why they have to be strong characters. Obviously my keeper makes a world-class save in injury time to keep it at 2-2. It was absolutely stunning from close range.
"It was brilliant but he was angry after the game about one or two things. He has supreme talent but I love his desire and drive.
"He is not basking in the glory of the save but looking at other aspects of the game and being disappointed in himself and that is why he is going to go all the way to the top."