I built my own set a couple years ago and after the cost of materials, tools I didn’t have, etc. it ended up being about $120 to make and took a me about 15 hours total (spread over 3 weekends). If I had to do it over again, I would probably buy the blank set as people suggested and paint/decorate myself. Would have saved quite a bit of time while still being customized.
That being said, you do have a little bit more pride in a set you built yourself. Also, I used 2x4’s for the base and legs and a ¾” laminate tops that I procured through work, so they are built like a tank and should hold up for a long time. A lot of the one’s you can buy pre-made tend to be a little flimsier.