Considering that they recently gifted a $10 voucher to anyone completing KYC identification, which can be spent on trading fees, and the number of these beneficiaries had to be in the thousands at a minimum, and possibly higher, it doesn't seem a comparative larger burden to giveaway a few hundred hoodies.
I suppose they must be getting good results? Binance isn't really doing all that stuff for the sake of giving, it's all to promote their platform so I guess it's the "why spend more when good amount of people are already falling for the tricks" kind of thing? We can also say that binance don't wanna spend much since anyone can see how dirt cheap a $10 worth of trading fees in exchange for KYC is...