One factor to consider is that not all ideas for Participatory Budgeting bubble up spontaneously from the residents of the city. Some are coordinated in concert with City Departments and their subdivisions in order to stretch the amount of money expended. Perhaps the greatest examples of this are the bike lanes and transit projects. I have heard City personnel on many occasions talking about how they were hopeful to get additional approval and resources for certain projects through the PB process.
The use of PB to stretch budgeting is not uniform across all City departments and divisions. For example, I don’t believe I have ever heard anyone from the Department of Public Works using this vehicle to stretch their budget — even though they end up being involved in implementing some of the approved proposals.