The Ben Ish Chai is very Makpid that you shouldn't do a Mitzvah without paying for it in Sefer Torah Lishma Siman nun if so when I go to my father-in-law on Pesach what should I do about wine and Matza?

The Ben Ish Chai writes there that there is a hiddur and it's better to pay for a mitzva, and accordingly, it's not that you must, but if you wish to fulfill this "hiddur", so you can pay your father-in-law for your share in the matza and wine which you eat.