If the vet thinks the rot is bad enough, he/she may be performing the blood work to see if septicemia has set in. Then again, it's usually apparent when it has...

That estimate seems really high. For comparison, I had a corneal abrasion surgically treated in a snake (complete with anesthesia, post of meds, etc.) for $700.00. $600.00 plus seems high.

I also had eggs removed from a gravid snake suffering from osteomyelitis and it ran less than $600.00...

I pay about $20 for a tube of the sulfa and an office visit can run anywhere from $35 to $50 depending on your zip code.