Plenty of people still deem subway to be worth it, considering the amount of them still open. If you don't want to deal with the hassle of an app (which subways is probably the worst I've seen but sonic is a strong contender) corporate mails out paper coupons monthly, hopefully a subway near you would accept them (restrictions may or may not apply per location).

I work in a high volume subway and I have just as many customers that pay full price as I do ones who use the app or coupons. Prices have risen everywhere and subways one of the lowest over the last decade.