Warning: Spoilers for The Mandalorian Chapter 1 (although if you still haven’t watched the first episode but have remained spoiler-free, let me be the first to welcome you out of your coma).
Disney seems a little bit caught off guard by the popularity of The Child; while Amazon has for sale unofficial designs and artwork, Disney’s best attempt is basically a screenshot printed on a cheap bunch of garbage.
I can come up with two excuses for this:
One, Disney didn’t want to spoil the big reveal at the end of the first episode by having a bunch of merchandise showing the character plastered all over it. Considering most businesses function on a for-profit business model, this seems unlikely.
Or two, Disney wasn’t prepared for the huge consumer interest in the character. They also missed the boat on Baby Groot back in the Guardian of the Galaxy days, so this wouldn’t be out of character for the company.
I expect it’s some mixture of both, but it’s an embarrassingly bad output of what appears to be a hastily designed money-grab. A white screen printed t-shirt for $25 is just insulting.