It turns out that refining and balancing a game with random elements (the items the "customers" carry) is quite complex and time demanding, even if it's a simple game with a simple mechanic. The random picking of items was way too simple(aka pick any one) because of time constraints, and this made interesting trades indeed hard to come by.
About the illogical trade of a ladybug for another ladybug + notebook, I guess Nina is just that charismatic and has mad bargaining skills ;)
Jokes aside, it is an unforeseen consequence of the way we rate trades as fair/unfair under the hood. I (who programmed the game) had to think for a while to get why this was happening... Thanks for pointing it out!
Fixing the above issues would take some extra thought and effort, but your idea of making "customers" leave after a while would be quite simple to implement and maybe make the game more dynamic.
As a little sidenote, I love that you referred to the traders in game as "customers", in quotes. We tried to distance the situation of the game from that of a "real shop", so you being uncomfortable in naming them customers is proof we got it right somehow.
Anyway, we thank you a lot for playing the game and sharing your thoughts!