Got him at stars count about 220-250, the only one frag at my server as far as I know and at least one more person went for 450stars.
If you need only 1 frag, spinning up to 200 stars isn't a bad idea, I had 28stars for x10 and that equals medium refine for 14-15cp (+ bonus Ay/scrolls).

Im sure theres something like this breakpoint, but most likely it cant be for every player since it would work like pulling with seal scrolls. It's just random, some people get it, some dont. This event has exceptional return for coupons in form of refine pricing (as far as previous (UN)luck star wheels are concerned). You may not like the event because it always *ed comparing to lucky board or general mobilisation, but if one needs/wants refines, 14-15cp is reasonable price.

One thing I have to agree with u is not going for it solely for any rare thats in the wheel itself, go for redeemables and if by any chance u hit the lucky point(tendo) in the wheel its just bonus. Bonus, not the main thing.