I can't tell you what it is, from that single pic, but I can tell you what it is not, and it is not one of the 1970s era Mauser Lugers. All those guns used the "Swiss pattern" frame, and IIRC were all in 9mm.
"Some parts replaced".. did they tell you that included the barrel?
I suspect it is a "Frankengun", a listing (pics would be best) of all the markings on it would help identify what it was, and maybe is.
$1500 is steep, but Lugers are a seller's market, and going prices have jumped again fairly recently.
Look in the Luger websites, they will have a better feel for current prices, and values (not always the same thing ).
If you have the cash, why not? They aren't making any more of them.