TOPIC:

I always wondered why "floss 47" costs 12000 pounds less then "SH 30" and found that the key is power!

You can also combine trains together like wagons, which increases their power.

Test result - 6 tiles trains goes from station 14 tiles:
1. "SH 125+goods vans pover 4563 speed 201" ends with 171km/h
2. "SH 125+SH 125+goods vans pover 9125 speed 201" starts faster but ends with 196km/h
3. "SH 125+stea SH 8P+steamSH 8P+goods vans pover 7807 speed 144" starts nearly like "SH 125*2", but after 7 tiles goes all the way with 144km/h

So the cost of company is hier with more fast trains. Cheat or a good use of game mechanics?

Multiheaded trains are a way to increase the acceleration and hauling ability of trains. Multiple engines are added to the same train to improve hill-climbing, acceleration, and cargo capacity.

Cheat or a good use of game mechanics?

You need to choose what you need.
Is it a single track with only that train, you could use the Floss 47 and save 12000 pounds.
And, you don't need to electrify your track so you can save a lot of money. (better for the city builder games)

If you really need a lot of power for heavy trains and steep hills, you can choose for the SH 30 and better. You need to invest a little bit more, but the trains will have a higher income because the goods are transported faster.