Yeah, but no amount of cost discounting is going to make up for a ship that doesn't feel useful on the field; if it's there in the game mainly for flavor, that's okay, but if it's part of a system where everything feels useful, not just in a by-cost sense but in the sense of actually having in-game synergistic capabilities (IE, fulfilling the classic cruiser role of being a fast, independent vessel with significant, though sub-capital, firepower), then there are breakpoints where no cost discount will make up for falling on one side of a breakpoint or not.
Even at 18 or 17 DP, I'd probably still take the Falcon; it's even cheaper, and even faster - and since neither one can stand up to a capital ship, I prefer the one that can run away better, hunt destroyers and frigates better.
I'm going to be a huge dork and quote Alfred Thayer Mahan on armored cruisers:
By giving this tonnage to armor and armament you have taken it from other uses; either from increasing her own speed and endurance, or from providing another cruiser. You have in her more cruiser than she ought to have and less armored vessel, or less cruiser and more armored ship.
If the Eagle stays at 50 speed, you could up-armor it, and get... well, the same species of disappointment you get in the Dominator, a classic 'armored cruiser' design. It's slow and clumsy for a cruiser, and it's still not quite capable of facing down a battleship. The Eagle is more like the interwar 'treaty cruiser'; a heavy cruiser with precisely limited armament.
Closing the speed gap would make the Eagle more generally-useful at cruiser tasks, while keeping it slow just makes it an also-ran, no matter how discounted.
