Dry burgers

besides fat content you may want to try and use worcestershire sauce when mixing the meat with your seasoning.  Gives a little more flavor and helps to keep ground beef and turkey moist

What grind of beef are you using?   Is it fresh?  Are you cooking frozen patties?

Yeah, frozen meat will kill your burger. 

If you don't grind your own beef, you should at the very least use fresh, never frozen meat. Freezing meat causes the water inside the cells of the beef to expand, bursting the cell walls and damaging the meat. In addition to creating a noticeable difference in texture (your previously frozen beef will be mushy most likely), once the meat is thawed the water will leak out rather easily since the structural integrity has been burst. 

If you run a dedicated burger place, I would recommend that you invest in a commercial grinder and decide on a blend of beef cuts you would combine to make a burger grind. A mixture of chuck, brisket (untrimmed), short rib, and sirloin would be a good start. Any or all of the above, with varying amounts depending on what you find you like. 

Other than cleaning, using a commercial grinder is a cinch, relatively quick, and would result in a vastly superior product for you. 

If you aren't using frozen beef, then it must be something in your technique or your ingredients. Are you over cooking them? Seems obvious...but I had to ask. 

Grind your own beef  if at all possible DO NOT USE FROZEN, it throws out water as it thaws.

    If you do grind your own try and do an 80/20 blend and grind the meat with ice cubes.

   This does 2 things  it helps keep meat stay at right temp when grinding as grinding builds friction therefore generates heat. and it will help keep meat moist for a longer time..

Another factor is te thickness of patties you are making. thin will be drier . Cut down on amount of salt sprinkled on as salt draws moisture out. If you buy meat aleady ground add water to it and mix it.

While it would be great if you can grind your own sometimes that is not feasible so follow some of the other great advice on here.  Don't use frozen meat, ever, for making burgers and definitely up the percentage of fat in your mix, at the very least switch to an 80/20 mix.  I even prefer a fattier mix closer to 75/25.  That does mean that you will get a bit more shrinkage, but I think the extra flavor and moisture is worth it.

Maybe they are used to the greasy flat top burgers.  I'll be honest here, I want a nice greasy burger and have little tolerance for "gourmet" burgers.  Good beef, high fat content, fresh ingredients is all.

One thing to consider is how the meat is handled by your cooks. Two things can lead to a dry, tough burger:

1- overworking the meat as you form the patties. This breaks up the protein and fart particles into ever smaller pieces and makes burgers tough and pasty.

2-cooks also tend to press on the meat with a spatula as it's cooking, either to speed up the process, increase the grill marked, keep them rounding in the middle or whatever. This presses out all the juice from the meat leading to a dry burger. Don't do it and don't let your cooks do it either. 

You are correct . A burger should be hand made if possible. it should not be compressed at all either when forming or when cooking.  If you do a good lunch trade with burgers and are sure you will use them all take the amount you think you will use out before the rush. They will cook better and quicker at room temp. And do not worry you are not going to kill someone for leaving it out a bit.