I usually use Fed Ex ground, I sell vintage, I need the insurance, it comes with $100.00 and anything over that there will be an additional charge. The package can bet tracked 24/7. If the shipping address is a business the charge is less, if the buyer lives in a remote section in the US the charge is about $2 to $3 more, that is what I have experienced. I get an e-mail when the customer receives it. If you sign up with Fed Ex through Etsy you get off 20% off. To me the piece of mind is worth it, vintage can't be replaced they are all one of a kind. I build in the additional cost in my prices to cover the bottom line. The news this week about the slow down of the USPS who knows how that will pan out in the Spring, when the changes take place.
I definitely agree with Sarah, get a postal scale, Amazon sells them for less than $20.00.
Good luck