Do not buy from a petstore unless you want your first ball python to die or at least have a difficult time nursing it to health. Ball pythons are in bad condition 90% of the time at petstores because most are not properly setup to keep a ball python in the correct conditions. There are some exceptions but if your new to ball pythons, you certainly wont be able to make that judgment. Plus, $70 for a normal I'm assuming, is way too much, most breeders are willing to practically give normals away. $25 is a fair price for a normal but if your willing to spend up to $100 you can choose from many beautiful single gene morphs. Of course they can go up quite a bit more depending on what morphs and how rare or how many are in the particular animal your looking to purchase.
By spring I should have many hatchlings to choose from. There are many breeders like me all over that do it as a hobby so depending on where you live, you may have a hobby breeder near you that you could get a far better price than a petstore and you will have a much better chance the animal will be in perfect health. Most hobby breeders take the health of their animals very seriously. You could also have an animal shipped from a breeder but if you think $70 is pricey then you will need to find someone local because shipping alone is usually $50-$60 so no breeder will find it worth shipping an animal out to make $10.