Should I buy my luggage in Korea?

Returning to Korea! I'm excited because I packed too light on my previous visit and could not take many things home. I'm debating buying a large trunk (I have two free checked bags with American) and a sizeable expandable carry-on to put inside with an empty duffel bag.

After my first visit, I realized how much I should have prepared luggage-wise, but I also saw how much cheaper some of the luggage was after landing. Would it be wise for my bank account and the sanity of walking up and down the train stations to stick to a backpack on landing and then purchase the checked bags to fill up?

Has anyone done this before, and have you had luck finding good luggage? I'm debating between Monos and July, but I decided to wait to see better in Korea. This Korean haul will include home goods, packaged foods, clothes, skincare, and souvenirs. I'll be visiting Sokcho and Busan, and I am a solo traveler, so let me know if you have done this and if it worked for you :)