"How much is that?"
What's a good way to figure out whether あの or あれ is necessary?
あの, この, その, and どの can't stand on their own and should be used with a noun following them. Use them when you need to talk about a specific kind of thing while drawing attention to the kind of thing that it is.
あれ, これ, それ, and どれ can be used on their own. Use them when the kind of thing you're talking about is already understood or easily gestured to.
If you're talking with a store clerk about umbrellas and want to ask how much a specific umbrella on the other side of the room is: 「あれはいくらですか」
If you're talking with a store clerk about things that aren't umbrellas (like wallets or something), see an umbrella you like, and want to know how much it costs: 「あのかさはいくらですか」
In real life it would be fine if it is obvious what you're talking about. But it's not a good translation of this sentence. 「いくらですか。」is just asking "How much?" But the question asked for: "How much IS THAT?"
I still don't get the whole are/kore/sore/dore deal. In most languages I learned there are only "this" and "that", and in Japanese there are four words I can't figure out how to use
Japanese distinguishes "this" and "that" by position to the speaker and/or listener. I was taught to think of it like this:
こ words (これ/この) refer to objects/places closer to the speaker than the listener. ("this [near me]")
そ words (それ/その) refer to objects/places closer to the listener than the speaker. ("that [near you]")
あ words (あれ/あの) refer to objects/places close to neither the listener nor the speaker. ("that [far from both of us]")
ど words (どれ/どの) are for questions.
Also the "no" versions (kono,sono,ano) are used in conjunction with the noun. I think they are considered posessive adjectives.
Kore, Sore, and Are are used alone as nouns. Unless you consider them used as "This (one)/ That (one)/ That (one over there)
"Are wa ikura desu ka" = How much is that (over there)?
"Ano isu wa ikura desu ka"= How much is that chair (over there)?