I am not plus sized, but I am very familiar with this problem. I'm 5'1", size 6 foot, with a 15" calf, so I'm a 6 XXW short. I've also asked about this before, and the answer is it's pretty affordable. I seem to remember people quoting amounts in the $50 range, depending on area. I bought a used pair of tall boots that had been heavily modified to fit someone similarly shaped, and they still look nice, IMO. They are certainly working for me and my budget right now since I cannot afford custom. You just need to find a cobbler in your area and get a quote.
Tug on anything at all and you'll find it connected to everything else in the universe.~John Muir