It depends on how much you spend on the game. If you only want to top up 5k ingots in a month or so, spending on WB Asuma is not worth it. Yes, it will give you more coins and more exp, but you can get much better value in lucky dice (since you're relatively low level the power gain from the summoning scrolls and such will be considerable) or treasures of the sages events buying refine runes. In fact, even spending the ingots for medium runes is even more worth it than WB asuma for that budget.
If you top up 5k ingots every week, then ignore the above paragraph, it is worth it for the reasons people are saying. Value is relative.
This is only my opinion though. What you c*so do is collect the frags from free this time, farm survival trial for hopefully more frags, and wait for another event or so to get it :).