That was the way that I interpreted your original post, that each hardway would be a separate bet and that you would have to make four bets of $5 each to cover all of the hardways, for a total of $20. Again, there is only one way to make each of the hard numbers and six ways to make a seven, so the odds are 6-to-1 and the bet pays 5-to-1, so the difference is the house advantage.
Marcr: to my knowledge, there is only one bet on a craps table where one bet covers multiple numbers and that is the field bet. I guess you could consider the pass/come and don't pass/don't come as covering multiple numbers, since they are affected by the 2, 3, 7, 11, & 12 but every other bet on the table covers only one number. Before someone says, "what about the horn bet?" that is actually four, separate bets (on the 2, 3, 11 & 12), which is why it must be bet in multiples of four ($4, $8, $12, etc). A "world" bet is simply a horn bet plus an "any seven" which is why it must be bet in multiples of 5 (one unit on each of the numbers).