This is so educative, and I have learn a lot from it. Come to think of it, cost is different from expensive just as you said. For example, as an entrepreneur, this two factors are very important in other to know if you're progressing in your business. To me, I see cost as the amount you use in purchase good while expenses is other sum of money spend either to maintain the product. If I buy Malta Guinness at the sum of $5 the expensive might be transporting the goods to my shop, etc. Well done.