In the end there's one thing that won't ever change. You always get what you paid for.
In the case of the knockoff/fake caps above consider that they come from a country (China) where this type of deceptive practice is looked at as a part of every day life. Exported goods are not required to meet any specific standards other than to "look" like the product being sold. Because there are no laws governing copied product the "duck" only has to look like a "duck", it doesn't have to quack.
Protecting yourself from this form of deception is actually easier than you may think if you practice some simple rules. Don't buy parts or products from an unknown source or supplier. Work with a trusted reseller and develop a relationship. Don't buy parts with names on them you don't recognize. Buy USA if at all possible.
Most people on this site are aware I rebuild Fender amplifiers and it's no secret that I use quality parts. I haven't polled anyone recently to check on the amps to see if there have been any problems, but I sleep well at night knowing I've done the best job I can with the best parts I can buy. I have developed a relationship with the good folks at Mojotone, a reseller/distributor I trust. They aren't the lowest cost reseller in the world, but you always get quality product, and I suggest anyone needing caps, etc. start with them. http://www.mojotone.com/amp-parts/capacitor-brands