There's a bit more to it than that.
You'll want to use a decent quality paper and have a decent quality printer to make anything that looks good.
Assuming you have a good printer and the right paper you'll also need ink.
Depending on how many of these you want to print it could be a LOT of ink. Ink is expensive.
Personally, I bought a case of UGCs and I download the images from thecoverproject.net and take them to a print shop to get printed and cut.
I haven't done a cost breakdown, but I'd honestly think that it might cost just as much to do the printing at home as it does to get the inserts printed out somewhere else.
That being said, I wouldn't go buy these premade cases unless I won the lottery.