I think it is worthwhile if you are familiar with the product you are buying. For example, if you were an air conditioning technician, you would know which units are better than others. You would know if you are getting a good deal or not. Even if you bought one that doesn't work, your experience would tell you it is an easy or difficult fix. Or, you could buy broken ones, fix them, then sell them to buy a new one.

If you are not familiar with the product, it may be a good buy or a bad buy. Without the expertise, you are relying on luck.