Just buy from exchanger and youll be safe, i mean you have chance to get scammed with this kind of transaction. And why do you think miner will sell his coin cheaper than exchanger does ? he can get more profit though if he sell at normal price and not cheaper.
That's correct. But I have seen people buying at less price and get more profit compare to exchange rates.
I don't have in-depth knowledge about their source of buying but its 100% true. They are doing something to get BTC at cheaper rate. It may not be from miner, that was my guess.
The best advise you can get is what the earlier poster has offered you and if you value your money I suggest you take it. Yes some people get bitcoin at a cheaper rate than exchange sites but they don't come to a public forum to announce it or even say their source as to where to get it from. The fact is any offer you get that is way below the range of the market price, is a red flag that is pointing to scam.
If you feel the exchange site are trying to reap you off, then buy from individuals if you know the gathering based on your location though or individuals on peer to peer site there you get offer from different people based how greedy they are to make profit and because of the embedded escrow system you are protected to a large extent. Aside that, when an offer is too good to be true, there is high chance its scam you need to be aware of that.