[DonRotolo]

A gusset or bracket CAN be cut with a hacksaw or coping saw. It takes a few minutes extra to do it completely by hand. Buy good quality blades, and finish the edges with a sander (or by hand with a file and sandpaper).

Holes are made with an electric drill.

One step up is a Band Saw or a Jig Saw. A few hundred dollars for a good one. be sure it can run SLOW enough to cut metal (Most run fast for wood, you can change a pulley to slow it down). A little more dangerous, but certainly OK for a typical high school student.

Another step up is a metal shear capable of cutting 0.090 or .125 aluminum. As you found, there are thousands of choices, some costing as much as a car.

Beyond that are milling machines, CNC Routers, and more, all in the multi-thousand-dollar range. I agree, asking your CNC shop to cut gusset plates is like asking your doctor to wash your clothes: You surely can do a fine job yourself.