Advanced-stage Parkinson's disease (PD) strongly affects quality of life (QoL). Continuous intraduodenal administration of levodopa (IDL) is efficacious, but entails high costs. This study aims to estimate these costs in routine care. 10 patients with advanced-PD who switched from oral medication to IDL were assessed at baseline, and subsequently at 3, 6, 9 and 12 months follow-up. We used the Unified PD Rating Scale (UPDRS) for function and 15D for Quality of Life (QoL). Costs were assessed using quarterly structured patient questionnaires and hospital registries. Costs per quality adjusted life year (QALY) were estimated for conventional treatment prior to switch and for 1-year treatment with IDL. Probabilistic sensitivity analysis was based on bootstrapping. IDL significantly improved functional scores and was safe to use. One-year conventional oral treatment entailed 0.63 QALY while IDL entailed 0.68 (p > 0.05). The estimated total 1-year treatment cost was NOK419,160 on conventional treatment and NOK890,920 on IDL, representing a cost of NOK9.2 million (€1.18 mill) per additional QALY. The incremental cost per unit UPDRS improvement was NOK25,000 (€3,250). Medication was the dominant cost during IDL (45% of total costs), it represented only 6.4% of the total for conventional treatment. IDL improves function but is not cost effective using recommended thresholds for cost/QALY in Norway.