Launch wouldn't qualify as a home grown player for us. Basically he's worth as much cap credit to Sale, as he is to us, with his missed games due to England duties.
Jack is worth more to us than others, unless he becomes an established durable international. Once a player misses 16 games due to being an international, they're worth the same to everyone.
Quick back of the envelope count would be that only 14? games are missed due to being and England player? 5 from Autumn (3 games, 1 prep week, 1 rest week), then 9 for 6N (5 games, 1 prep week, 2 mid tournament weeks, 1 rest week after?). So upto £70k (£5K per missed game for England internationals), max home grown and intenrational allowance on a single player is £80k.
So having done all that, a home grown player, who's an established England player, is perhaps only worth £10k more to his home team, though it will vary.