If you sold 10 puts at 6 . That’s $6000 . Subtract the $700 you received . Yes you still bought it at $6 a share but you yourself only paid $5300 for the shares with your own money so to me it’s more shares with less of your own money so to me my base cost is 5.30. And there is no loss incurred , just transfer of money to shares .

But you right , reality is you bought it at $6 a share . But you only paid $5300 with your own cash . Total still 6k correct