A spear is a better weapon than a sword, here is why they have all these bronze spearheads on sale on ebay.?

I don't think it's really in dispute? Back when people fought wars with melee weapons, spears were always the dominant weapon type, including variants of it, such as the javelin, pike, lance, or polearms. As you correctly say, the reach is a powerful advantage and will outclass a sword in many situations. Plus they were cheap, easily replaced, didn't really need any maintenance, and it's an easy weapon to learn. You can line people up in rows, with a second row holding their spear through the gap between two people in front. The Romans did it, the Spartans did it, and the Greeks did it. Rows of swordsmen would all get in the way of each other when they start swinging, and a back row is stood idle waiting for the front to get killed.

Single handed swords (arming swords) were a backup weapon. They were easily carried, much more easily than trying to carry a replacement for your main weapon. People who primarily fought with a sword weapon, used huge two-handed blades that most definitely could compete against a spear. They were also expensive and much harder to master.

You could compare a sword to a modern handgun, people carry them because they are light and can be concealed if necessary. But a soldier will have a rifle and the handgun will be their backup sidearm.

I've seen people who are good with spear and shield and it seems like it is about as good as sword and shield in duel, and better than spear alone.

Depends on what era that derive from and who used them. And in what war

Sword is much better for defense and close combat! Sword also has much larger surface area for deadly impact! Spears are great, but only with an expect levels of skills!