The most difficult thing to buy were the weapons. If they had the option, Harry and Hermione would have forgone them entirely to instead use their wands. But, not only would nobody feel threatened with wands, but using them would break the Statute of Secrecy in a way that would ensure the Ministry of Magic would shove their arses in Azkaban at the first opportunity. They wanted to rob stores and banks, but they couldn’t attract the attention of the Ministry doing so.