priceless

Short definition from Wiktionary

Adjective

1. 1
   Without a price assigned; unpriced.
2. 2
   So precious as not to be obtainable or sold at any price.
3. 3
   Of no value; valueless; worthless.
4. 4
   Held in high regard; treasured.
5. 5
   Absurd; ridiculous.
6. 6
   Very amusing; hilarious.
7. 7
   Excellent; fantastic; wonderful.