In terms of chords and melody, Expensive has complexity on par with the typical song, having near-average scores in Chord Complexity, Melodic Complexity, Chord-Melody Tension and Chord Progression Novelty and below-average scores in Chord-Bass Melody.
Expensive is written in the key of F♯ Dorian. According to the Theorytab database, it is the 8th most popular key among Dorian keys and the 42nd most popular among all keys. The F♯ Dorian scale is similar to the F♯ Minor scale except that its 6th note is a half step higher (D♯). Chord progressions in Dorian have a characteristic sound due to the major quality of the chord built on the 4th scale degree. See the F♯ Dorian Cheat Sheet for popular chords, chord progressions, downloadable midi files and more!