When did shipping cost become more than the gift?

Ok, so I made another diaper cake for my cousin in California...it's to be a decoration for her baby shower. With all of the business of life, I got a hint behind, but I got it done, checked the internet for prices to send it...I figured it was 7 lbs (close it was almost 6) and USPS says it'll be $18 for priority and it'll get there Friday (perfect! the shower is Saturday). I take the box down to the p.o. and the very nice gentleman behind the counter tells me $30ish and it'll be there Saturday OR Monday, he's not real sure...ummm...excuse me? That's almost DOUBLE of what the internet quoted...well then what will get it there ON Friday...ok I can go Express and of course on the SIGN they GUARANTEE MOST places the NEXT DAY, but apparently not MY place...but it will make it there Friday afternoon...for $40...so I ponied up and paid it...ouch! I wish I could say I procrastinated, I didn't, but really...ouch!