What is the difference between retail price and cost price?

Retail price is typically the maximum price that the item would sell for in a store. Cost price is what it actually sells for.

So what does your question have to do with your "budget income statement"?

If you are more clear about what you are looking for, we might be able to help further.

I think within the context, "cost price" is probably referring to the company's cost of the item to buy it, versus the retail price which is the selling price. And yes it would be relevant to a budgeting income statement because both numbers would appear on it.