In the Avengers Volume 1 Number 9 we see the introduction and “death” of a new character named Wonder Man. Spoiler, Wonder Man comes back later on.
The story is fairly simple. Baron Zemo, aka the Executioner is working with the Enchantress to destroy the Avengers (because that’s gonna happen hahha). They attempt to do this by finding some charges being filed about financial embezzlement which they attempt to blame on Tony Stark.
Eventually they stage a battle against the Avengers in which Wonder Man comes to the aid of the Avengers to earn their trust. The bad guys in this case come very close to defeating the Avengers when Wonder Man decides to save the Avengers because they did attempt to save his life at one point. Wonder Man, predictably, saves the Avengers and then ends up being killed by a fatal dose of poison.
How much is this comic worth? Well who knows. It really depends on condition. They tend to sell anywhere between $20 and $1,000. Mine? Oh who knows, it is sitting in a box and not going to move.