I routinely can't find good prices on 6 AWG or larger copper wire. Typically I end going to West Marine, and getting it there. Getting a little tired of bending over at the cash register and uttering "thank you may I have another".
I mean it is great wire , and I use it on my boats , but I don't need fully tinned marine grade.
Where do other people get wire ? Not a box store, unless you like being frustrated and having clerks that might have a seizure at your request,
(edit... this is for stranded, not solid)