USPS shipping option has been disabled for US orders but is still available! 

If USPS shipping is cheaper than UPS we will still ship via USPS and adjust your shipping cost accordingly (unless you enter alternate instructions in the Ordering Instructions" box).

Recent USPS back end shipping system changes have caused massive shipping cost irregularities. For international orders regular mail service option should still appear but could be wildly inaccurate. 

Only PayPal orders charge immediately. Credit orders are charged later during the shipping process.