Okay then, let's break this down to the bare minimum of needs.
Plain warm water to soak his feet in for a good 15 or 20 minute soak, after soaking, gently yet firmly dry his feet with a dry terry-cloth towel/rag, the type that has a rough texture often used for bathing. The texture of this cloth will help to loosen the scabby portion of that wound, and with luck, it will 'pop off' during/after one of his soaking sessions. Cost... your time.
After his warm foot bath and gentle/rough drying with a cloth, put a little bit of cooking oil into the palm of your hands and massage that into his legs and feet (both top and bottom of the feet). This will also help to moisturize his skin and improve blood flow to his feet and legs, making them healthier in that regard as well. Cost... a penny plus your time.
Doublecheck other members of the flock's feet and legs for mites, and if found, give them a foot massage with oil too. They will not require a complete foot bath for this treatment. For a few pennies, can treat the whole flock.
Now that I understand your situation better, I can read your past messages differently, and apologize for my judgement of you.
The advice given to you will cost nearly nothing but your time, and in my opinion, is sound advice. Failure to heed the advice given risks the health of your entire flock because of the mites and in particular, this rooster, with his added risk of sepsis due to the bumblefoot.
Keeping you and your feathered family in my prayers.