The number of ways to pick 5 different numbers between 1 and 75 without regard to their order is 17,259,390 combinations. So you'd need this many dollars to buy all the combinations!
To get this number think of picking one number out of 75. You now have 74 remaining numbers. Pick another and you have 73, and so on. Combine these for 5 numbers: 75*74*73*72*71=2,071,126,800. But this number includes the order as an important factor. This is a permutation, and this permutation is going to cost about two billion dollars! However, if the order doesn't matter, then we have to divide this number by 120, which is the number of ways to arrange 5 different numbers or objects. This gives 17,259,390 combinations.