What makes you think that these cost-benefit analyses are not being done by municipalities and related agencies all the time? Roads require upkeep and revision

What makes you think that these cost-benefit analyses are not being done by municipalities and related agencies all the time? Roads require upkeep and revision of their layout as a matter of course, or else London would still predominantly feature cobblestone roads suitable for broughams rather than SUVs. Any action they take will 'cost something', even not doing anything (lack of repairs will cost you double in the long run). Don't worry about 'funding by the users'. Cycling is a net-positive for population health and government goals (exercise as well as less congestion and pollution); by that logic users should be paid for riding a bike! Besides, most cyclists pay taxes already; or are you advocating charging pedestrians for the use of pavements as well?