Yep. I do this with iTunes as well. I typically save $10-$20/month on my Prepaid cell service by using refill cards that I buy on sale or BOGO. I also saved over $150 by doing this on my last Disney vacation. Costco, Target, BJs, etc. have good regular deals and often great sales on these.I have posted here before the advantage of using gift cards to pay for OTT services and use them to get a discount on those services, every year between Black Friday and x-mas gift cards go on sale between 20% off ( itunes, google play, sony ) to 40% off (netflix, hulu, hbo, cbs, et), I stock up every year and plan to do so this year.
itunes for example this week are 15% off at Costco so I bought a couple of $100 packs to cover buying 4K movies, I also wait to buy till 2 weeks after disc street date, then itunes makes new 4K movies $9.99 which turns into $8.50 for me because of the cards.