AT&T has cut its price on refurbished 16GB iPhone 3G units, dropping the price by $50 to $150, or a savings of $150 off a new unit. In February, AT&T lowered its pricing on refurbished iPhone 3Gs to $99 (from $149) for 8GB models and $199 (from $249) for 16GB units; the pricing on 8GB models remains unchanged from this prior drop. As with new iPhone 3Gs, the refurbished units require a two-year contract, and AT&T notes that all refurbished…