Lob-Ster 501 tennis ball machine, $5.

Tennis ball machines like Silent Partner, Prince, Tennis Tutor and Lob Ster, all look different, yet all cost a fortune. These machines can be an opportunity for you because they're so unusual that most people have no idea what they are, yet so valuable that they can make your week. Why not learn more about tennis ball machines so you'll know them when you see them?

The humble little Lob Ster tennis machine is a perfect example of the fact that in this business, there's very often more to the picture than appears at first. Like most all tennis machines, the function of this Lob-ster is to shoot tennis balls at you as you attempt to hit them back, and I guess lots of tennis courts have them because practicing by yourself would be much more difficult without one!

This machine actually tripped me up at first, because when I first saw it I mistakenly thought it was some sort of wet/dry canister vacuum cleaner. Your mind and eyes can play tricks on you if you're not careful!

Although I had no idea of the value of these machines when I found this older Lob Ster, I figured that for $5, I'd just take my chances.

I've said it lots of times already and I'll say it again. Always plug the machine in, and heck, fire a ball or two through it if you can. Make sure the darned thing works like it's supposed to. And be sure to check for damage. These machines are often tossed into vehicles to be hauled to and from the courts, and you don't want any surprises later on.

And as it turns out, this most basic of Lob Ster units costs almost $800 new, and this one sold on eBay for a cool $355.

Photo of Lob Ster tennis machine