"Таксі - дорогий транспорт."
Translation:A taxi is an expensive means of transportation.
"транспорт" looks much more like it means "means/mode of transport", from the way it's being used here. In English we don't speak of a bus, train, taxi etc being "a transport", so these English translations are incorrect.
In Ukranian it's also rather "вид транспорту". Транспорт - "a set of means intended to move people, goods, signals and information from one location to another".
In American English, it's all called transportation. Transport, I believe, is used in British English.
Nouns in English use articles. "A taxi is an expensive transport." Or, the most common usage would be "Taxis are expensive transportation." The plural of таксі is the same.
the last comment below is quite correct but when I offered "the taxi is an expensive form of transport" I got told I was wrong and it should be "The taxi is an expensive modes of transport." This is quite simply formally grammatically incorrect. It should be at least 'mode' (singular) not 'modes'. But 'mode' is a very formal word, the kind of word used by bureaucracies rather than commonly in daily speech - so 'form' is actually better: it means the same thing and is more street-friendly. But actually better again would be "taxis are an expensive form of transport" or best of all "taxis are expensive"