60 per tile is not that much when you consider a standard 160 Km/h express track is over 20 a tile (over 40 if elevated or bridged). I guess it comes down to how much monorail makes per tile compared with trains.
According to the speed bonus window, monorail with 100 km/h generates the same income (per tile and passenger) as tram with 100 km/h or train with 180 km/h (in year 1998). So, the maintenance costs are that much
because the income is not high for monorail transport.
If you use the fastest monorail train available in 1998 (PMNV TC-1; 100 km/h max.; 82 passengers max.), you'll get 0,06 C/(tile*passenger). That's 4,92C for a full train per tile. The maintenance costs are 0,29 C/km which seems to be the same as 0,29C/tile. That makes 4,63C/tile profit per full train. So you'll have to transport 16 full monorail trains per month to cover the maintenance costs of the monorail tracks (70C/tile). That's 1312 passengers per month which is a lot. If you can't keep up such a flow of passengers, the maintenance costs will quickly burn your savings.
Comparison to tram: With tram MHz T-235 (90 km/h max.; 78 passengers max.), you'll get 0,05C/(tile*passenger). That's 3,9C for a full tram. The maintenance costs are 0,74C/tile. That makes 3,16C/tile profit per full tram. So you'll have to transport 5 full trams per month to cover the maintenance costs of the tram tracks (14C/tile: 10C for the track, 4C for power). That's merely 390 passengers per month.
If the maintenance costs for monorail tracks could be reduced (e.g to a third), it could become actually possible to make profit with monorail tracks. With the current costs, building monorails doesn't make any sense.
PS: A standard 160 km/h rail track has only maintenance costs of 12,80C (instead of over 20C) if you don't need electric trains.