So I can spend $2800 on a water heater that has questionable reliability, requires a bigger gas line, and will save me 40% off my $18 a month water heating bill?
Yes. I've thought of it, but no, it is not a good idea.
I think your pricing is a little off; my parents have had a Rinnai heater now for more than several years with no reliability issues and spent far less than $2800. Even Amazon has them priced much lower [1].
