No, I do not believe I am losing money on shipping.  Example: 3/25  I paid $3.09 to ship something back.  I  was paid 2.77 euros, which is $3.09.  I use Paypal to purchase the postage - one of the few online places where you can actually pay for 1st class pkgs - anything under 16 ounces.  I turn those shipping bags inside out & reuse them!  Yes, there's tape & gas, printer paper....  I have that with most other projects, too.    I try to only ship Mon/Wed/Sat.  For those donations, I use a flat rate box & jam pack them.  I also stack eBates for the rewards on donations & if absolutely necessary, use my Chase card & get points.  I have saved every email a lead or "zazuu" has sent me about $$$.  I will reiterate that even if a shop is rejected, shipping fees ARE reimbursed.  Ok, more info than you asked for, but there ya go.