The pathways for receiving a diagnosis of a rare type of dementia are poorly understood. Diagnostic challenges decrease access to relevant health promotion activities and post-diagnostic support. This study was focused on pathways experienced by people affected by rare dementia in Wales, United Kingdom (UK), considering the practical, emotional, and economic consequences. Semi-structured interviews were completed with 10 people affected by rare dementia across Wales, UK (nine family caregivers and one person living with rare dementia). The interview data were subject to a thematic analysis and a bottom-up costing approach was used to cost the pathway journeys. Five transitional points occurred across the diagnostic pathway (initial contact, initial referral, further referrals—provider, further referrals—private, and diagnosis) alongside two further themes (i.e., involved in the diagnostic process and disputes between stakeholders). The timeliness of the diagnosis was perceived to often be subject to ‘luck’, with access to private healthcare a personal finance option to expedite the process. Higher economic costs were observed when, in retrospect, inappropriate referrals were made, or multiple referrals were required. The confusion and disputes relating to individual diagnostic pathways led to further emotional burdens, suggesting that higher economic costs and emotional consequences are interlinked. Clearer diagnostic pathways for rare dementia may prevent unnecessary service contacts, waiting times, and associated distress. Prioritising appropriate and timely service contacts leads to diagnosis and support to families and enables people to increase control over their health. Appropriate diagnostic pathways may be less costly and reduce costs for families.