Yes, they may have been able to get somebody like Dahntay Jones, or somebody similar, who can contribute as much, if not more, than Giddens this season.
The problem with that strategy, though, is that you're without question sacrificing your future. If you rely on a strategy where you forgo rookies, and rely only on cheap vets, three years down the line you're left with a team that has no youth, and an aged "big three". At that point, no free agents want to join the team, and we're limited in our building blocks.
It's good to have low-cost / cost-controlled, high-upside players. I'm sure Danny assessed the situation and determined that Giddens can help now, and he liked his potential. That's good enough for me.