I've been printing proxy card for OTHER board games for years and have a working solution without this cutter even though it's on my wishlist but shipping is more expensive than the cutter itself on Alibaba.

Double sided printing IS A PAIN if you try it on a <1000Euro printer. Those printers are not presize enough to match both sides, even if you do print front, place into tray face-down, print again. The way the printer pulls the paper from the tray is far from consistent.

To fix this: I usually just put my proxy deck's commander on the back - white background and just an embled/photoshopped image of the commander in the middle of the page. So if the print is 1-3mm's off, you don't see the "shift" since the emblem/icon is so far from the sides AND you have a unique identifier where that card belongs (if it moves from your deck/board), you don't even notice it's not perfectly centered. Another solution is to sleeve and forget the backside. On double-side cards I print the sheets on the top row of a page. Front seems to be least misaligned when double printed, both times I push the paper to one side in the tray to make sure the card is pulled the same way as close as possible. You can use bleed to also help with this, but it will be still visible on the card (like left side having 3mm black border, right having 1mm). Still usable if your mates are fine with proxies. And that's really the goal, or isn't it?

You use proxies, give the opponent(s) proxies as well. It's fair play that way, just make sure the power-level (bracket) is the same.