Tools
In an emergency, cheap tools are fine but spending more on these items is always worth it. After all, everybody wants pieces of equipment which can last them at least a couple of years.
Batteries
Batteries that are available in dollar stores tend to run out quickly since they are typically poorly made. Modern formulations are not used in a lot of them. These batteries might also leak. When it comes to batteries, it is definitely better to get brand name ones instead.