Also, you can notice how Haesoo got a little bit uncomfortable with the materialistic action of Taeha because Haesoo has another priority to use the money for. I could relate to her situation, but I know she deserves new stuff. She'll get used to Taeha's love language soon. ^^
I'm glad you brought this up, because it was similar to what I was thinking. They both have different pasts and upbringings (which they both need to talk about and explore in due time.) Although, it seems as if both were abused during their childhood, he still comes from a rich parent, while her family was poor. Abuse victims, especially those who come from a poor economic standing, are always in a state of "need". And oftentimes, it is the abusers that put them in that state through manipulation and control of assets and the environment they exist in. But due to the abuse that they constantly receive- which can also take the form of financial abuse- they learn not to ask for anything, and do without, so that way those moments of "relying on others" won't be weaponized against them later on. I have personally lived this, and have seen it play out often in domestic violence cases (especially in family and romantic relationships). Abusers often use the victims moments of need to keep them victimized and trapped.
Even though abuse victims mature and move out of their circumstances and find freedom, the mentality of doing everything through their own power and money, in addition to not relying on others out of fear of betrayal, is hard to break. Also, subconsciously they don't want to owe anybody anything in case it gets used against them later. They will always feel the need to pay people back even if something was a genuine gift. A lot of simple and innocent gestures become a burden on to these people in their own minds because of past trauma. To get over that requires a lot of healing, patience, and love. Taeha is going to have to be very patient with her while being consistent and showering her with love that she's never had before until she gets accustomed to it. She's going to feel very awkward and uncomfortable being a "receiver" because her instincts are going to be constantly worrying about the "bad" that might come around the corner later.
Everything's not enough because not everything is absolute for the both of them, Taeha and Haesoo. She's not used to him buying her stuff because she never felt that way in her previous relationship, her ex never initiate her on a date, etc. However, Taeha is PRIVILEGE unlike Haesoo, he can buy whatever he wants and he can make everything go on his way. There's a huge difference in their social life and the way they both live and I think that's the most obvious gap in their relationship right now. It's not that they don't understand, I think they just need a little more time to focus on each other. (LoL i psychoanalyzed them HAHA)