I think your test data is close enough as is for anyone to draw a conclusion about how much your choice in BSO commuting is costing you. If you find that the original pedals are unsuitable for commuting and replace them the replacement cost should be added, it hardly makes much difference.

I think the bottom line on bike commuting costs/savings is that big $/€/£ savings come to an individual if bicycling for transportation purposes allows the individual to reduce the number of cars owned without suffering a significant loss in transportation mobility or quality of life. The savings can be magnified if bike use allows the cyclist to eliminate very high daily car parking fees associated with parking in expensive cities like NYC, London or SF.

The costs of any bike (if reasonable) and upkeep are relative peanuts compared to the fixed/variable costs of car ownership and use.