I graduated in 1972 and got a pretty card. No money for frivolous stuff like graduation gifts... When some of my (rich) acquaintances, who got things like trips to Europe and new Plymouth Dusters for graduation presents, asked me what I'd gotten, I'd reply "a card" but kinda duck my head and say it low so it sounded like "car".
You give what you want, what you can afford, and what is reasonable. What those are may be different for everyone.
My son is graduating (high school) this year. I've made sure he understands that *anything* he gets as money or gifts is a bonus to be appreciated, nobody owes him anything, and if somebody tucks $1 into a card they send, he writes them back (using the $1 to buy a stamp) and thanks them for their thoughtful gesture. He gets it :)