Back in 1990, the St. Louis Blues signed future Hall of Fame defensemen Scott Stevens as a free agent. As compensation to the Washington Capitals, the Blues had to give up 5 first round draft picks to the Capitals.
In 1991, the Blues signed future Hall of Fame forward Brendan Shanahan. As compensation, the New Jersey Devils demanded Scott Stevens and won him in arbitration.
In 1995, Brendan Shanahan was traded for future Norris trophy winner and MVP Chris Pronger. While not a Hall of Famer yet, he's considered a strong candidate for the Hall of Fame. (Edit: He was inducted into the Hall of Fame in 2015).
So if you're following along, effectively the Blues give up five first round draft picks for Stevens, which led to Shanahan (although unintentionally), and then led to Pronger.
If Pronger indeed makes it to the Hall of Fame, the Blues would have effectively given up five first round draft picks to get 14 years out of three future Hall of Famers.
The Blues were incredibly smart or (likely) incredibly lucky that these string of signings and trades could net them three future Hall of Famers.
Was it worth it? Well, on the one hand, many first round draft picks end up as busts. While some of those first round draft picks led to quality players like Sergei Gonchar, it didn't net the Capitals any significant progress towards a Stanley Cup. The three players weren't able to get the Blues a Stanley Cup either, or even a trip to the Conference championships.
Many teams have done way worse with their first round draft picks. Getting 14 years of Hall of Famer performance is probably way better than you could do on average with draft picks.