The printers using the HP 78 are old and dated but why should a customer trade in a printer that is so economical to run? These printers are work horses, unlike Epson and Canon where the print head is on board the printer, in the models that accept this cartridge the print head is  actually on the cartridge. This means that every time you change the cartridge, you also change the print head. Epson and Canon have print heads that degrade in quality as they wear out.   On the other hand HP 78 printers such as the 940c will print beautifully for many years until the printers die!  
 
The other factor is economy, we sell this model at around $16.90 delivered to the door with much larger discounts in quantity, the equivalent cartridge from HP runs around $40.00. Compare that to the the newer model cartridges like the hp 97 and the Hp 57 which only have around  14 ml to 17 ml of ink and sell for more money.  A High Yield remanufactured  HP 78 holds 38 ml of ink (Double the ink) and is around 30% less in price.  When comparing to purchasing new the savings is even greater, around 1/2 less in price and double the ink. No wonder so many buyers keep the printers accepting this cartridge until the printers drop and in this age of throw away electronics even have them repaired!
 
There are two types of HP 78 cartridges (aside from the original) available on the market. New generic third-party knockoffs and remanufactured original cartridges,  We are going to concentrate on remanufactured cartridges because new generics not only have a reputation for inferior quality, but also are in violation of trademark laws, and have questionable legality. You can recognise the New Generics when the listing has the words "NEW NON OEM" 

Let’s first concentrate on the re-manufacturing process 
The most important factor in creating a quality cartridge is the empty. Remanufactured cartridges are dependent upon the finding of an empty cartridge. If the empty cartridge is crap the final result will be crap.  In guide #2 we'll show the manufacturing steps.
 
When a cartridge is used only once by an end user, the empty is called a virgin empty.  A virgin empty in the spot market, will sell for five to 10 times more than a non-virgin empty.  The term non-virgin means that the cartridge  has been refilled more than once, so it's no longer virgin. Each time a cartridge is used the print quality degrades so naturally a cartridge that has seen more than two print cycles is going to print very low quality. Also mechanically it will be more likely to break, have a worn circuit board, burnt nozzles etc. On the other hand a cartridge produced from a virgin empty will print beautifully. One of the ways to recognize inferior product is by price, if the price seems too good you are probably purchasing an inferior product.
 
It's a shame that so many consumers don't realize that there is a world of difference in remanufactured cartridge quality. They buy the lowest-priced cartridge, have a bad experience  and then say "remanufactured cartridges are lousy I'll stick with the original".  An additional caveat is that the seller who sells this junk has such a high return rate that he can't  provide decent return service.
The very cheap HP 78 cartridges that you see in the market are  remanufactured using non-virgin empties.

The manufacturing product, process and the materials used are very important for determining the quality of a cartridge.  The lowest of the low we call "Drill and Fill. Drill and fill cartridges are cartridges where the company simply drills three holes in the cartridge injects ink with a syringe closes the holes and may or may not print one copy. These cartridges, will have low print quality, and have the highest level of RMA (Return  Merchandise Authorization) incidence, regardless of whether a virgin or non-virgin empty is used.
 
Another factor vital to cartridge quality is the ink.  A professional remanufacturing company will only use ink that is specifically designed for the cartridge that is being remanufactured.  A Drill and Fill Guy or amateur will use universal ink, unmatched ink, or the cheap Chinese stuff.  It is very important to use the correct ink, not only for color matching, but because the print head will only function well when ink with the right viscosity is used. Specifically in printing with any inkjet cartridge the ink is squeezed through a nozzle.  If it's the wrong consistency  it will clog the nozzle or it won't flow right. At the best the resulting color reproduction will be shoddy and at the worst the cartridge will stop printing very early in it's lifecycle. The best inks are manufactured in the United States, Germany and Korea (Our re-manufacturers only use American Inks).  The cheapest ink comes from China which is notorious for its inconsistent quality.
 
Another differentiating factor in the re-manufacturing process is the remanufacturing machinery.
In the professional processing of the HP 78 at the least a centrifuge machine is used for cleaning and a vacuum based fill machine is used to fill the cartridge.  These machines cost thousands of dollars. Your amateur simply doesn't have the money to make this kind of investment in machinery. If not cleaned properly and filled properly the chance of receiving a poor cartridge increases exponentially.

The best remanufactured HP 78 Cartridges will be made from a Virgin Empty, filled with a Quality Color Matched American or Korean Ink, and undergo a thorough manufacturing process using state of the art machinery.