Here’s an example of what the boot upgrades look like using Plated Steelcaps:
Free Tier 2 Boot Bonus: +5 Armor
Tier 3 Upgrade: Costs 750 gold, but provides +5 Armor, +5 Movement Speed, and a new unique passive that, after taking physical damage from a champion, grants the owner a physical shield for 10% of their maximum health for 5 seconds (with a 10 seconds cooldown).
Why though? The winning team already gets a big gold lead, why give them even more buffs?