The leaking hose should be replaced as a whole unit. Yes, you have to pay for a new charge of freon again, the AC shop will totally drain your freon charge. If they have a recycling machine, they can temporarily store your freon charge into that, replace the leaking hose and re-charge your own freon, adding if necessary. But I still have to see an AC shop that uses a recycling machine, apart from the big casa's (I may be wrong though). And lastly, the price of the hose will depend on how long it is. Most AC shops sell hoses by the foot.