Coils are priced from 4500/-. Depends on the Brand. and it directly linked with the cooling capability. Cheap ones are Korean ones and Malaysian ones. U can replace a cheapest coil and fill up gas after cleaning the system for less than 12k with R134 gas, Including Filter. Hope u r other parts are working fine. Better show u r car to another place. Ask for a quotation. So u can get an idea. The main factor in the coils to get leaked is the rust. cause is dust which absorbed mainly from inside the car. A/C shop ppl recommends to service the A/C systems once a year. So rust can be delayed somewhat.