Well - T-shirt, $20. Strings, $10. Truss rod cover - call it $10, but it's as much a memento as anything (I've never put one of the Sig Club TRCs on a guitar). So that's about $40. You get 10% off purchases through the Lifestyle Shop, so YMMV on how much that's worth to you.
There are occasional Sig Club events. That's only useful if you're in that area and you can go, but if you can, how much is something like that worth.
For me, the opening night event at Experience, which is exclusive to Sig Club members and their guests, is worth it to me. I've seen Carlos Santana, Buddy Guy, David Grissom and Mark Tremonti, among others, at the event. Again, YMMV - the artist every year is not necessarily to my taste, but I'm one of hundreds of people there.
More important is that it's an extra night to hang around people who have become friends, and it's a very low-key evening. Sure, there are two additional days to hang, but Friday and Saturday are a little busier.
That's what makes it worth $60 to me. YMMV, and no one will (well, no one should) have a problem with that.