It's all of those things. Generally, a lower tier skate meant for beginners is going to use lower quality/less advanced materials leading to being heavier, less stiff, lower durability, and resulting in lower cost. There are usually price points associated with each tier.
Here's a more thorough description of the tiers: https://www.icewarehouse.com/lc/skates/how-to-select-an-ice-hockey-skate.html
The $300 price point is usually a low to mid price point in other brands so that's why I said it's hard to tell where these skates fall. I didn't say that they ARE beginner or intermediate skates (although they may be), just that it's hard to tell. When you put a product in an established price point, people are going to think it's of similar quality. Maybe some shop owners would know better.
Being a once piece boot doesn't automatically make it premium skate. I'm sure they could make the same once piece shell out of plastic. And fiberglass isn't that special.
I agree that it seems like the TF7 provides a lot of bang for the buck but who knows.