That solder job is hideous, for one. I am actually in the EXACT same boat, as near identical happened. The solder jobs on my former piping were absurdly clean. Artwork. ABSOLUTE ARTWORK! Now look what has been introduced into the system.
Original work:
View attachment 27176
Replacement:
View attachment 27177
That said, I was installed the same make and capacity hot water heater as what went bad, and all parts and labor total was only $100 service fee. It is 30% more efficient, as well. I looked it up and the unit was $700ish. My home warranty really pulled weight. The guy just asked how old the heater was (15 years), and he said "Yup, you probably need a new one regardless, I'll order it". and that was that.