The sentences in this lesson feel incomplete; it might help if at least some of them had an additional clause to make them more explicable. The sentence above seems to imply that "ustedes" do in fact "tienen dinero," but that they would not if it were not for some other factor e.g. parental support.
You've learned that wrong, I'm afraid. There's no such thing as a formal "they"--Ustedes is the plural way to say "you". In much of the Spanish-speaking world, it is both formal and informal. (Duolingo follows this usage.)
Just as "usted" uses the third-person singular form of the verb (the same as for "he" and "she"), "ustedes" uses the third-person plural form of the verb (the same as for "they"). That does not make it mean "they," though.
I have listened to many other programs that teach Spanish and find that duo has the worst and at times impossible to understand! They should have Speakers from Spain who enunciate correctly, were learning Spanish, not Mexican or central or Cuban etc. If wr learn Spanish correctly we can go to any Spanish speaking country and converse.