If Scotland get independence, then the simple fact is that prices for goods and items will go up. Companies will claim doing business over a border costs more and their prices will reflect that - bit like how UK based companies try and justify the price of goods in Ireland, when just over the border in Northern Ireland it's much less....
One thing that is very high in Ireland is motor tax - it's 3 times more expensive here due to the much lower density of cars (and a historically greedy Gov.). There's 5m people in Scotland driving x% of the UK cars. Motoring costs are bound to increase - tax, insurance (no doubt as claims per pop. and crossing an international border now into a diff jurisdiction would change), the forecourt price of cars would go up.....
I just can't imagine the costs will remain the same. Independence at a price.