Non-academic is a simple neutral statement of allegiance. Non-academic experience is one you gain outside of school. Non-academic license for software is different than "software for educational use only".
Unacademic is inappropriate for academic standards. A paper that calls upon results of Tarot readings as source of prediction of construction durability is unacademic. The theory of Intelligent Design is unacademic.
In many contexts, the meanings are pretty much the same, but you might hear finished more often than completed in casual conversation. For example:
I've finished my shopping.
She finished the song.
He finished the race.
I could use completed in those sentences – the meaning wouldn't change, but the register might sound off.
The word completed can convey some sense of accomplishment. In the context of a race, it might work when the race is a major achievement:
He completed his first marathon last year.
Homework, though, is not really a major achievement, so I think you'd hear finished more often in casual conversation:
“Joey, where are you going? Did you finish your homework?”
That said, you might see completed in more formal contexts, such as a paper on education, or a course syllabus:
Students must complete six homework assignments during the semester.
Best Answer
The short answer: when used as a noun, the "price" is the amount charged for something, and the "cost" is the amount paid for something.
When a person is discussing buying something at retail, the most common noun used for the amount charged by the seller is "price."
When used as a noun, "cost" refers specifically to the amount paid by someone for something. It is most often used in an accounting or business context.
It is not exactly wrong to use "cost" as a noun in the same way you would "price":
However, this is not as idiomatic, at least in American English; it sounds a bit melodramatic. You would be more likely to use "cost" as a noun where it is understood that you are discussing the impact on your finances, rather than the amount the store asked for the item:
Confusingly, you can use "cost" as a verb to describe the amount charged for an item:
"Price" as a verb is used only for the act of setting a price: