You'd be better off picking on something else for your project. There is no such thing as an anti-AIDS drug.
If you mean AIDS treatment drugs then it's a continuously moving field, and you can't compare what was given 10, 20 years ago to what is given today because the drug regime is constantly being optimized and modified as new treatments are brought into play. It's not a single drug or treatment, it's a regime.
Retrovir or AZT was the first drug which is now out of IP protection, like all drugs it costs $200M to $800M (depending on what it's for) to bring a drug to market which you also need to take into account. Maybe 100M for a well understood painkiller to $1B for anti-cancer and complex treatment such as required for HIV/AIDS
Because IP protection is withdrawn after 20 years following the application the early drugs are out of protection compared to the newer drugs still under protection and have a vast price differential for that reason.
Sorry, you asked a simple question but it doesn't have a simple answer. For a simple answer choose something like paracetamol. You can make the same point and you know your talking about like-for-like