Just wanted to know what calculation the game uses to determine the buy and sell prices of items?

What is speechcraft worth?

What are the prices for items when you have no perks or speechcraft?

Do perks stack on speechcraft and each other for example does 10% better prices from opposites six stack on the 10% - 30% better prices perk, or does it only stack on speechcraft or the base price (whatever that is).

Trying to determine if smithing ever become profitable from bought materials...