I believe that using star coins for Sunday Storm satellites is the best value if you're good at playing poker. Buying stuff from the shop isn't a good idea if you ask me. Well it's just my opinion. I never use re-buy option in any of the tournaments i'm playing, and so far i've spent 120-150 coins to win 2 Sunday Storm tix(divide it by 5 to get the number of attempts) Cashed one of these tickets into $32 in the main event. So for let's say 150 coins(1.5$) i've played 30 satellites and 2 sunday storms, won $32... That's the best value i think, because majority of the players in this satellite play it like if it's a freeroll.
But in past i've spent thousands of coins to buy tickets directly.