If you're on such a low budget as $7K I'd say go with the 35mm DSLR systems if you're into getting the best performance for your money, and go for a second hand MF system if you like the old-school handling of these systems or just like to have something different. Don't expect it to be better in a technical aspect though, except for possibly some particular aspects like lens bokeh or something.
I have an ancient Aptus 75, the image quality is just fine with that, but sure it wouldn't hurt with the DR you get from an A7r in some difficult lighting conditions in my landscape photography, and sometimes higher ISO and longer exposure would be nice too. However, I just love working and make images with my Linhof Techno, and well, to do that I must have a digital back and I chose one that matched by budget and had good performance in absolute terms.
The message is that if you buy a budget MF system it's generally not for imaging performance alone, it's for that you like to use the camera.
If you shoot landscape I think a tech camera with movements is what really makes the MF experience fun, the shooting experience is then so much different from a regular DSLR. The attached snap I shot yesterday using my Linhof Techno and SK72mm Digitar lens, it has 15mm vertical shift, 2 degrees of tilt and 2 degrees of swing. Couldn't have done that with an A7r (oh well, perhaps I could, not sure about tilt-shift lens availability, it's less flexible than a Techno for sure though). Not the greatest image perhaps, but just a few hours old example of when I used shift tilt and swing in combination.
I have six lenses in my system, all with very good imaging performance, all with at least 90mm image circles, all bought second hand. Compared to buying Otus-type of lenses new my system is actually quite a bit cheaper, and the second hand MF market is quite good.