Teams usually overpay when they're bidding against other teams. That's how that goes. That's why a 4th liner like Gaustad fetched a 1st. That's why a 3rd liner like Hanzal got a 1st and 2nd in 2017. When you're bidding against other teams, the price always goes up. Look at free agency every year. Dumb contract after dumb contract.
GM's don't operate the way we armchair GM's want. They value production and performance more than futures. The main thing most posters here on HF want is as many 1st round picks and prospects as possible.
I agree, it's supply and demand. It just so happens that this year there is a lot of supply. I'd be very upset if the Flames gave up their first and didn't go after one of the bigger targets, or at the very least a younger player than Zucc that will likely stick around with the Flames. Also, how many teams are willing to give up their 1sts and outbid the Flames?
In terms of upcoming UFAs, there's also Stone, Duchene, Panarin, Simmonds, Eberle, Ferland, Hayes, Silfverberg, Nyquist, and a slew of other players the Flames could target that aren't upcoming UFAs. Zucc may be better than some of the players on the list, but the difference to the Flames, who are looking at acquiring their 5th best forward (max) is pretty marginal. If it doesn't mean giving up the 1st, I'd prefer the slightly worse forward option. The Flames are either going big (which I doubt), and getting a guy like Stone, or they are looking for a 3rd liner and 2nd PP guy. In which case, they may be better off with a Boyle type than a Zucc type.