Just a guess, but from reading the info @ that link, I’m guessing we’d be at around $300 there, more if a pump this old has more parts needing replacement. It may be worth a call to them to see what they think.
I seriously looked at rebuilding the pump myself, but I just don’t know if I have the finger dexterity, for one thing. At almost 70 y/o, that’s slipped some, for me. Even handwriting has gotten more difficult. :-( (!!)