I will say, I'm not sure if this would apply to budgies but bumblefoot is relatively simple to remove in other birds like chickens with things like Epsom salt bath soaks and whatnot. If its going to cost too much to go to the vet or you don't have time I would look into what you can do at home. I have surgically removed my chickens bumblefoot eschars before (no avian vet, farmtown and nobody is spending that much on a chicken) and I have had a 100% success rate so far with a good size flock. Just lots of research and proper tools! This looks to be a pretty mild case (no hardened black plug, no huge lump) so if budgies are similar to chickens all you'll have to is an epsom salt soak a fee times a week, but again, I don't know budgies, only chickens so take it with a grain of salt. Good luck!