The paper is only indirectly about parking spot monetization. Dr. Shoup's bigger concerns (as I understood them as a student in his undergrad class at UCLA in 2005) were:
(1) optimizing for availability: price high enough that some spots are always available,
(2) real-time pricing: based on demand throughout the day/week/year, and
(3) avoiding externalities from subsidy or under-pricing: make parking as hard/expensive as it should be and other transportation modes seem a lot better by comparison
