I'll go in order:
Personally, I think Smith is the one we can least afford to lose. Me might be a dodgy operator, but the last couple of weeks, as well as the 2008 GF have shown how valuable he is for us. Apparently, he is on around $600k (including brown envelopes). Cooper Cronk is also imperative to our success, and there's no other halfback I'd prefer for the money (apparently around $350k, which is negligible).
Billy Slater is a good player, and helps us across the line, but not to the level of the other two. Inglis is problem though: he can be the best in the world one day, but be a spectator the next. I'd love to keep him, as he plays well when it really counts, but as a centre, he's not quite as critical as 1, 7 and 9. I think him especially will command big dollars from elsewhere, so that helps our cap in the future too lol.