Sadly, it's pretty much ruined as an intact item and you're correct that cost outweighs value for professional restoration.
Another option would be to buy an unsigned 52T Mize of similar condition. Then, make a clean vertical cut close to the tear and place the signed portion on top of the unsigned card. I'd personally leave the two cards loose/unattached in any way and just display stacked atop each other. It would provide the easiest and nicest aesthetic. It looks like the cost for another card would pretty much equal the price of a roll of the archival tape people are recommending, so perhaps consider which of the two options appeals most to you.
With the way the card has ripped, it looks pretty much done for to me. Any amateur attempts at putting the pieces back together again will turn out to be a messy endeavor IMHO. It will look amateurish and Frankensteinian, if that's even a word.
A third option may come along via this board. Someone reading might have more experience with this sort of thing and may offer to assist in the reconstruction. Considering this card didn't break the bank (and I'm trusting you were refunded for it, anyway), this may be worth trying. If you're unhappy with the results, you could always go with my first suggestion afterward.