Your opponent cannot use a disarm action to disarm you of spiked gauntlets. An attack with a spiked gauntlet is considered an armed attack, unlike the regular gauntlet.
The cost and weight given are for a single gauntlet.
Simple, Light Weapon
Cost: 5gp, Weight: 1lb
Dmg (S): 1d3, Dmg (M): 1d4, Dmg (L): 1d6, Critical: x2, Piercing
Source: Player's Handbook