You do get 7 free drops per day, over the course of the week that's 42 more to come (more if you haven't gotten all the free ones for today) which would save you 800 coupons compared to getting it right now. So the overall cost might be closer to 3.5k if you are willing to wait a bit.

I think that's a reasonable price for this clothing, especially considering you also get other stuff.

That said, as always, clothing is for higher powered player who have reached serious diminishing return elsewhere. So I'm not recommending it for everyone. But if you are aiming for clothings, this is a good enough option.

That said, due to the higher you go better the reward mechanic, I would NOT recommend using this event for partials. Either have 4k+ in the bank and just get it (perhaps on last day or something to save a bit) or skip it. Spending 2k and get a third is probably not worth it.