In Kiddo's world it is.
I should back up; this is all about teeth. Kiddo has lost a total of three teeth now and a fourth is wiggly. When she didn't put her last tooth under the pillow, I asked why -- she said she wanted to keep it because it was hers, after all.
This week she has gone one better. She wants to write a letter to the tooth fairy requesting her other two teeth back. When she was reminded that the tooth fairy paid her for the teeth in question, she said, "That's OK, she can just send me a bill."