Actually, the problem is the fact that the virus hides in a type of cell that lives in your body for a good 50 years or so. As soon as drug therapy stops, the virus goes back to work replicating and destroying in the process.
With most viruses, infected cells are recognized and destroyed. However with AIDS, I believe the problem is that the very cells that direct the immune system are the ones that are infected, which short circuits the process.
As for vaccines, the virus (HIV) that causes AIDS is very tricky and mutates it's "appearance" so it is no longer recognized for what it is by the antibodies produced by the reaction to the vaccine. It's basically the same reason there is no cure for the common cold. At least you can't catch it from a sneeze.
As for the drug companies, they are in business to make a profit. There is nothing wrong with this, assuming that the company behaves ethically. AIDS research is extremely expensive and if the companies cannot earn enough money to recoup their research and development costs, they have no incentive to find effective treatments. Everything costs more initially until that R&D investment is earned back.
On the bright side, there are some vaccine trials occuring now that show some promise. However, there is no guarantee that they will succeed given the difficult problems that must be overcome.
The bottom line is that the best "cure" for AIDS is to MODIFY YOUR OWN BEHAVIOR SO YOU DON'T BECOME EXPOSED TO IT. This is the reality. The drug therapy is better than nothing, but it is difficult, unpleasant, expensive and for the rest of your life. The process the drugs use to inhibit the virus really screw up your natural biological processes and so you trade one illness for another that at least is not fatal.
Use condoms, practice that sensuous touch darlings, and remember that no sexual experience is worth your life.