Margaret Jusinski first got to know her investment broker through the breakfasts he provided when he visited her public school in the leafy suburbs of New Jersey, where she teaches middle-school children computer coding and how to build robots made of Legos.

After the bagels, muffins and coffee, the broker made his sales pitch — and Ms. Jusinski bought it. So did many of her colleagues.

The teachers only recently learned how much those meals actually cost them.

Had she been able to choose a simpler, less expensive plan instead of the broker’s costly offering, Ms. Jusinski would have approximately 20 percent more in savings, according to an analysis performed for The New York Times. One colleague would have a balance 50 percent fatter. The list goes on.

“It is a heartbreaking situation for everyone,” said Ms. Jusinski, a mother of two girls who turns 50 on Sunday. “Especially for the staff members who were looking to retire within the next few years.”