The USP and USPc are what I would consider the standard or more accurately the older models. HK45 and HK45c are newer releases and similar to the P30 model but with side mounted safety's similar to the USP line. In my area $650 to $750 range for new USP's depending on features and $850's and up for the newer HK45 models. I can't comment on the features and benefits of the HK45 but have owned both the USP and USPc in 45 and would recommend the compact for carry purposes. Full sized USP is a very big gun.
$1075 for a USP or a USPc is to much but might be normal for the newer HK45c. HK makes some excellent products but if I'm going north of a grand for a handgun I'm looking at high end 1911's, custom Sig's, etc. Your prices on the XD line seem high to me (top end with night sights should be about $585) but again that is in my local area on the left coast not yours. I'm sure some one more familiar with both models will way in with better advice for you.