"一共五百块钱" is also correct, but it's marked as wrong here.
Would 一起五百块 be fine as well, or not, and why? :)
一共 = sum up, 一起 = together with person
一起 = together with a person
五百块一共 should be accepted as well.
No, because adverbs always go before any numerals
There's no "Altogether it's..." in the Chinese. This is not the best translation.
一共 means "altogether it's "