Those maintenance costs (52p/68c per commute) include:

1406 km / 873 mi / 28 GBP / 46 USD

Rear tire worn through canvas - replacement needed
1 Schwalbe Lugano
1 Tube
1 10min tube swap service

1559 km / 968 mi / 13 GBP / 22 USD

banged rear rim on kerb cutting a corner short
1 new tube
1 bend rear brake track with adjustable spanner
1 10min tube swap service

1597km / 992 mi / 28 GBP / 47 USD

Split Schwalbe Lugano in half with only 191km on it
1 Gatorskin tire (cost of Lugano refunded)
3 new tubes (one used)
1 10min service

1789 km / 1112 mi / 30 GBP / 50 USD

Front tire worn through canvas
1 new gatorskin tire
1 tube used (second of three)

2119 km / 1315 mi / 4 GBP / 6.8 USD

Flat rear tire and front bake pad replacement
1 pinch flat after leaving bike in locker and riding without inflation (last tube used)
1 set of new front brake pads

2177 km / 1352 mi / 1 GBP

Tape for bars

3132 km / 1946 mi

Slightly ruptured Gatorskin on road surface and lost a tube

3511 km / 2181 mi

Fully ruptured Gatorskin
Replaced with a Schwalbe Marathon and 3 extra tubes

18 JUN 2017

Rear brake rusted ... cut cable ... pulled cable and lever off ... kept caliper on to hold fender
Swapped bars and tape as above
£0.13 for a new cycloputer battery

Recently another cycloputer battery (25p total)

Summary: Those costs seem reasonable to me as the road condition in northern England are really tough on tyres (bikes and cars).