My first 1.8/50 was the same. Only "fog". My repairman disassembled it. He could remove 1/3 but not completely. It was no oil or perspiration. The surface of 4th or 5th glass was incurable damaged by fungus.
At my 2/35, I had that kind of "spider web" fungus. Very little, just in the outer area, hard to detect. This my repairman perfectly removed. The lens is clear like a crystal again
110 USD is OK for a try. But not for me.