Is it ever sensible to appear in court without a lawyer?

When is it sensible to appear in court? It's a risk/reward proposition.

If you're charged with a crime, DO NOT REPRESENT YOURSELF. In fact, shut your mouth.

But Small claims court was designed to be accessible to nonlawyers. In a regular, more formal courtroom, sometimes it's also a good idea to represent yourself. Hiring a lawyer is almost always unaffordable for disputes that involve less than $25,000 and often unaffordable for disputes in the $50,000-$100,000 range. In these cases, representing yourself may be your only reasonable option.