You can look at this two ways, 1. You can make a custom pit to your exact specs or 2. Buy one that is close enough. That is the difference in the cost. More on reddit.com

You’ve stretched too far from the supply. You can only push so much gas through the hose and the further you go the less it will carry. Shorten your hose and you’ll see more flame. More on reddit.com

Burner/air shutter may not be adjusted properly causing unburned gas from the burner. A picture of the flame would be helpful. More on reddit.com

Reason it's expensive, its made of 304 stainless steel. It will last outside and you won't have to replace every year or two. It wont get clogged and it is made to look like a firepit. I sold these at my last company and it really is the way to go if you want it to last but there are much better options that still keep cost down and simplify everything. If it was my project, I would used a stainless steel outdoor fire ring, connect with a dante key valve for shut off with flex lines to connect them. Add a spark igniter made for a grill that is battery powered. And build a base from stone brick and cover. the holes in the burner need to face down! Otherwise they will clog or get filled with water. Also keep in mind the gas type as you want a yellow flame and not blue. Turkey Fryers are made for heat and not looks they mix the air differently. Price should be: SS Firering $70-$90 depending on size, Dante Valve $25ish, Igniter Kit $25ish This way you do it right once and it will last. More on reddit.com