If you have a coin pocket or sub pocket inside of a main pocket it is a great place to carry a folder.
anything smaller than a Delica compromises your ability to use it if it's used for anything other than opening envelopes.(if it may have a tactical use )
The stay close to bias of a lock back is much safer to carry inside the waistband then almost anything else except for a knife with a secondary lock.
Inside the waistband under a belt is not very fast to draw from.
A low-carry pocket clip will make the knife much more discreet.
For your budget you could have two delicas and two low carry Lynch pocket clips.
If you want something that is pimp get a small Sebenza. For double your budget it'll do almost as much as a $70 Delica.
For whatever reason people often suggest knives that they're looking at themselves that have no practical purpose for what they are going to be used for. I am looking at this from the utilitarian purpose of stay closed bias.... slim.... quality materials and great ergonomics.
A 3 inch bladed knife does not freak most people out.