I buy SMA connectors a couple of thousand at a time from a chap I found on ebay in Hong Kong who still advertises there. About 0.25% are dodgy, where the metal finishing hasn't worked, so swarf remains and shorts, but it's usually visible during assembly, and of not it shows up in test. I wouldn't take them up to 18GHz, but they're fine for my application which is up to L band. They work out at about $0.25 each when bought in that volume, so as you can understand, I'll take a 0.25% failure rate at that price thank you.