They need to make lots of it to make their risks worthwhile. Keeping drugs pure costs money, so its not a very important consideration to dealers. Side effects include jittery feelings, irritability and palpitations. More serious side effects include sleep problems and decline in appetites for food and sex. The most serious problem is that these drugs are very addictive.
Stimulants produce exaggerated feelings of energy, alertness and well-being.
Unfortunately, when the drug effect wears off, a corresponding period of exhaustion and depression sets in. These effects reinforce a desire for more drugs to combat the low feelings. Side effects include slowing of reflexes and reactions, slurred speech, impaired judgment and blurred perceptions. These effects make it especially dangerous to drive. People feel that they are performing well when in fact their abilities are impaired.