Well, that's always a good sign if you keep looking at it - it means it should be worn! In terms of cost, I'm really not sure because a man's ring always has a lot of gold and this would have to be made for you because it's not calibrated (and looks a monster of a stone)! If you went with 9k yellow gold (very hardy and durable) and it was about 10g of gold, you're probably looking at £350-£500ish but that's very much a guess.
The one thing I would add is that I wouldn't be tempted to go frou frou with this at all because the stone is so large that you want it to be the centre piece and adding any other stones will just disappear against it (unless you use a tons of other stones and then the price will go through the roof)! If I were making this into a ring for a man I think I'd go for a closed back yellow gold bezel (again, this will help the stone to show it's yellowness and where the stone is losing some of it's colour in the centre, it'll combat that).
Hope that helps?