I think some people here may have misunderstood some of the OP's information... or maybe I am :) It sounds like a repair guy came out and replaced 2 pounds of refrigerant. It could have been R22, but I suspect it was R410 as the AC is only 5 years old and R410 isn't nearly as expensive as R22. Installing a R22 system just 5 years ago would be malpractice in my opinion with it being banned. This top off of the refrigerant probably cost $250 or so. Then the OP stated it would cost $1500 for a repair. I suspect it was implied this would be the cost if a major component needed to be replaced. If it’s a simple hose leak at a solder joint, that would be repetitively easy for a tech to identify and fix. $1500 to replace an evaporator isn't bad given the industry. I had a Lennox evaporator coil fail in under 3 years on a new unit. Very disappointing. Lennox supplied the parts at no charge but I had to pay for labor and refrigerant. It was about $1500 many years ago.
Assuming you know no history on the unit as you just acquired the property, I would wait and see how long it takes for the leak to cause another issue. Maybe it’s a very slow leak and you won't need to touch it for another 3 years. Even if you do need to touch it, its maybe $250 a pop for a refill. If you do need to refill it within a year or to, have the technician also diagnose the leak. If it’s a simple fix, they can resolve your issue right then and there. If it’s an evaporator or condenser, it will be a more expensive fix, but still a fix none the less. I'd rather pay $2k to properly fix a 5 year old AC than pay double or triple that for a new system. Just make sure you have time before the warranty expires. If it expires soon, get the leak traced before it’s too late.
Also, most people don't seem to know this, but when an AC dies of old age, the AC needs to be replaced. Not the entire unit. Here in AZ, the AC and heater are usually in one package. I had an AC die and got 4 estimates. They ranged from $7200 to $9500. Then I got a 5th estimate from a local guy. He took a look and saw the blower fan was fine and the heater was also fine. Only the AC part was bad. He charged me $4200 to completely replace the AC. So, my lesson was don't fall for a slick sales guy selling you a whole package. Only get the AC replaced if that is all that is bad.