When Booster first arrived in the past he didn't know what idioms were, he often took them literal. Such as "shake a leg." He didn't know where to use a credit card, didn't realize his accountants didn't pay his taxes, mistook 60s music as modern and didn't know how do dress for a PR. date. That said he never came off as dumb. Impulsive at times but he was still a smart businessman shown building his empire. Of course he also had Skeets to correct his mistakes but over time he got used to the changes.
Then we have Starfire, a character that has already been on the planet for some time. Her guides were Dick Grayson then Jason Todd and Roy Harper. In RHATO she showed no cultural shock. Once she flew ahead of the boys, got herself a new outfit and met them in a limo. They knew nothing about it beforehand so how could she go from that to not understanding the concept of banks? How did she do that or get new outfits? Is this supposed to mean others provided for her? She does not get that old people die. Kori was a princess, a slave, a freaking space captain and she never met/heard of anyone that died of old age? This implies she was pretty damn sheltered when evidences proves otherwise.
Even if the Starfire series is ignoring her time in RHATO (kinda hard to do since she talked to Essence) I call bullshit. Kori still spent time with Dick and Roy (Secret Origins confirmed this.) The Sneak Peek even had her knowing people she never met in the new 52. I don't care if their superheroes she would pick up on this stuff. Banks get robbed in superhero books. She would likely hear the news. Hell Lobdell implied she could pick up on more information than just languages when she kissed someone (see her attempt to do so with Jason.) Then out of the blue she gets a memory loss? I mean that is what happened, right? It had to be some kind of amnesia if she can't understand these basic things anymore.
She doesn't get sarcasm despite using it herself in the past? Thinks an enemy that nearly killed her and her boyfriend is someone who will give her friendly advise? Starfire shouldn't have cultural shock at this point, not with things this simple. With celebrities, movies, even music? Sure. But this makes it look like she came to earth then spent all her time in a cave. Judging by Dicks' costume when they were together she's been around since Jason was Robin.