It is similar to how both sentences would make sense in English - if you drop the 钱, the context is still implied.

这个多少 - How much is this? 这个多少钱 - How much money is this

钱 - money

这个多少钱？would be more specific that the topic in discussion is about money. 这个多少 like How Much Is It can have meanings other than about money, but is so often used that it can be easily inferred to a request for the price. Actually we have also omitted the verb in this sentence, which is probably 卖/sell.

You said "How much is this", and the full five characters is like "How many dollars is this". Essentially the same thing in this context. But you can use yours for different situations because it is more general

The last character means money so it's "how much does this cost" v "how much money does this cost" but the sense is more or less the same.

多少 refers to how much while 钱 is the word for money. If you were asking someone a question about a specific item, it would be assumed that you are asking about the price, not how many there are.

The last word just means "money." So if the context makes it pretty clear you are talking about money/cost, you can omit the last word.

It's alright.