The cost of making only the maker knows, Valueless if bought, but sometimes traded. A poor man may give one as easily as a king. When one is broken pain and deceit are assured.

Common Wrong Answers
“Gold”
Gold has intrinsic value and can be bought or sold, which contradicts the idea that it is 'valueless if bought'.
“Gift”
A gift can be valuable and is often given with the expectation of appreciation, which does not align with the riddle's emphasis on valuelessness and deceit.
“Secret”
While a secret can be traded or shared, it does not involve the notion of being 'broken' in the same way a promise does, nor does it imply the same consequences of pain and deceit.
Similar Riddles
Riddles you might also enjoy
What gets broken without being held?
I am free yet priceless, you can't own me but you can use me, you can't keep me but you can spend me. Once you lost me you can nev...
People need me, but they always give me away. What am I?
Whoever makes it, tells it not; whoever takes it, knows it not; and whoever knows it, wants it not. What is it?