Is there a good database comparing the cost of public transport? I found this one and this one but they cite no sources so have no idea how they were constructed. Also, it is for a given period. Ideally the database should have more years. I've searched in OECD and world bank without success. Help please! :)
The world bank group has a Urban Transport Data Analysis Tool (UT-DAT) located here: https://www.worldbank.org/en/topic/transport/publication/urban-transport-data-analysis-tool-ut-dat1
It has an excel file that has some data. There is also Data.world https://data.world/datasets/transportation
There is Global Mass Transit website but its a paid service with some free options: https://www.globalmasstransit.net/index.php
This Wiki site here might be a better option for you on free public transportation data links: https://www.transitwiki.org/TransitWiki/index.php/Publicly-accessible_public_transportation_data
The world bank has Public private partnerships investment in transport (current US$). Which are contractual relationships typically between a state or local government, who are the owners of most transportation infrastructure, and a private company.
This looks like a hard find.