When people come to me asking how much to weld this or that I tell them I don't know. The reason is each job has it's own specific criteria, such as fit, preparation, purpose, intended use, and expectations. The hoop on a cycle seems pretty simple and for the most part is. But if the welder runs a business he has liabilities and will probably want to do the job right, which involves bevelling the two edges for more positive penetration, using a slug or pig to bridge the weld to ensure strength equal to the strength of one continuous piece of tube. Using a pig requires holes drilled in the frame to allow the pig to be welded back in away from the seam. All this adds up in time and materials, and from the welder perspective that money. Yes he could just tack the hoop in three or four spots to hold it in place then run a bead all the way around without the bevelling or pig and say there you go, leaving the cycle owner to clean up the weld smooth and pocket 20 bucks and forget it, until a year later when the weld potentially fails and the family comes knocking on his shop with legal action sighting responsibility.
I know we are talking a hoop and what are the chances, but smart businessmen have to think this way in order to protect themselves and their reputation. I weld myself and I have a saying that I follow religiously on all my builds, "If it is a structural part that must not fail get it welded by a certified welder, because you can't sue your own ass if and when it does!" Yes this is a rant and I don't want to start an argument over who's right or what are the chances. I believe if you want to create a custom ride, but can't afford to do it right then DON'T start, cheatiing, taking chances, doing it on the cheap, sooner or later will come back and bite you in the ass. :-\