Not sure. I know they push tons of deals through the apps. I know this second-hand, including from someone who routinely gets entire meals from Taco Bell, specifically, for a couple dollars—just as you used to be able to do off the normal menu. Sometimes he can get absurd amounts of food for less than a dollar—just as you used to be able to do couponing or deal-hunting. In short, what it looks like to me is the normal prices became "sale" prices, the former sale prices became super-duper-sale prices, and the new menu prices are a totally new massive-profit-margin category that didn't exist before.
This is actually pretty similar to what pizza chains have been doing far longer and to a greater degree than other fast-food joints used to—it's long been the case that you can get 30-50% off your chain pizza order with coupons, and that there are always a bunch of coupons available to suit many common orders, such that there's rarely a reason to order anything at full menu price from a major pizza chain unless you just can't be bothered to track down any of the deals (hence, it's price discrimination, with a side of psychological manipulation to make you think the "deals" are actually bargains when they are, rather, simply not rip-offs).
As for my own experience: we usually do Arby's when we want garbage food. We can easily drop $40 there at menu prices without going nuts—or we can get all of the exact same stuff for $15 or less, with coupons (the key: lots of their coupons list, in small print, a count of times you can apply it in the same visit, so you may be able to use a single coupon for, say, "$3 sandwich + fries" to buy five of those meals at once at the coupon price). Again, these places have long had coupons, but they didn't used to constantly have lots of coupons or other deals active at once, and the difference between coupon and menu prices didn't used to be so extreme. Actually, noticing that Arby's prices had damn near doubled over just a couple years (pre-pandemic) was what prompted me to take notice of this situation, which does appear to be playing out industry-wide.