Yes, there is a Cat 7 standard for 8P8C, it just uses the GG45 plug which is backwards compatible with RJ45. There are no Cat 7 cables terminated with RJ45, they are terminated with GG45, otherwise they can't be called Cat 7.
I think you missed my point. GG45 is certainly backwards compatible with RJ45. But if you find pre-terminated "Cat 7" cables with RJ45, which many stores do sell, they are not Cat 7. In the cases I've seen, they are just Cat 6/6A cables marked as "Cat 7".
However, even if you cut the GG45 connector off and put a RJ45 on the end, the cable itself is still better than Cat 6/A cables because each pair is shielded and the whole cable is shielded with another layer of shielding on top of that.
I agree that it isn't worth spending extra on Cat 7 cables unless you have a very specific reason that needs Cat 7. However, Cat 7 cables are started to get pretty cheap too, you can get 10ft Cat 7 cables for under $5 each these days. So it's not like it's a huge waste of money if someone buys Cat 7 over Cat 6/A.
It depends if you're comparing apples to apples or not, i.e. comparing a minimum spec U/UTP Cat 6A or S/FTP or F/FTP Cat 6A to Cat 7 (with the same wire gauge). To really find out whether the cable is truly better you need to dive into the data sheets, and hopefully they are tested with comparable test parameters. They may very well be the same cable with a different certification, or have a very insignificant difference. I would argue there is not much point in buying a cable certified for 600 MHz vs. 500 MHz., unless you find one that's certified for much higher speeds than that.
Edit:
I also want to emphasize that the Ethernet standards are very conservative, so when 10GBASE-T allows up to 55m on Cat 6 and 100m on Cat 6A, that has taken into account a noisy server environment with hundreds of these cables next to each other. So unless you plan to coil your network cables around a fridge or run it past an induction cooktop, using a good Cat 6A cable that exceeds the minimum requirements will be plenty good for 10G in any home, and possibly shorter runs of 25G in the future.
It's far more important that cables are properly terminated and not physically damaged, than going beyond Cat 6A.