No need to make the price a range as there is only one sale. You could likely make the price 75 flat - valuing the Didgeridrongo at ~3 keys, which should be fine ± a few keys due to rounding.

If you want to get a more accurate (and likely slightly higher) price, you need to "mini" the Didgeridrongo. Essentially, provide sales for the Didgeridrongo that can prove a specific value for it, and that price can be added to the 72 keys to price this hat.