I decided to give this a try, and I thought I'd chime in here with my experience and math.
tl;dr: As the others, particularly JVV, have said, for someone who has something they do for a while at around the same time every day, during which they don't need their phone for anything else (or have a spare device whey can use for watching the video ads) and can spare enough attention to tap a "show another" or "close" or "right, show me the next screen of the ad already" button every so often, it should easily be possible to cover the $15 plan this way after the initial payment; in fact, it looks like with adequate diligence it should generally be covered by the third week of the month.
As already commented, the "daily" aspect of this is not a midnight-to-midnight window in some time zone, but a 24 hour timer since your last time. As far as I can tell, that applies separately to your check-in, your spin (which has an actual countdown on it, so it's the easiest to keep track of), and to each of the 25 video ads you can watch per day. So if I log in and spin right after my spin timer ends, and then watch ten ads, and then stop to do something else for an hour before watching 15 more, then the next day after I watch my first ten ads I will find no more available until an hour later when the cooldowns on the remaining 15 start to expire.
Obviously, this means the 7-day streak counters for spins and videos can't mean you spun 7 times in 168 hours. There has to be some leeway in how long you have to continue your streak, because you can't continue it until the 24 hours are up. I haven't figured out - and I hope not to, really, because why would I want to break my streak? - whether you have another 24 hours, making the streaks effectively "at least every other day", or if it's the next midnight in some time zone after your cooldown runs out, in which case there would be some time of day at which it might be effectively impossible to continue a streak if that's when your last spin was. The former seems more likely.
This cycle also means that the time you're earning will inevitable crawl at least slightly later in the day over time, which will eventually result in a "month" having fewer earning days than actual days, when you effectively skip a day to get your timers back to the beginning of your earning period. To allow for this, I'm basically treating all months as 28 days, which I think should be overcompensating for this phenomenon in my case.
It also appears to me that because you can watch more than one video ad per day, but you can only spin once per day, the 75-coin bonus for a seven day streak of spins is in fact every seven days at the best, but you can finish a streak for videos and then immediately start the next one, so that you can actually complete a video streak every six days (after the first one). I'm not accounting for that in my math, and for someone really diligent about putting in their earning session at the same time every day it could effectively mean an extra 75 coin streak bonus every month, so that and the fact that you can get better than the minimum spin value just make the whole thing work faster, even before factoring in surveys or "offers."
I've done a few surveys, but there's always the temptation to go for the ones that show a large reward, and I'm demographically boring enough that I usually get bounced out of those early. Meanwhile, the low-reward ones don't seem like a good return on my time, especially when they aren't necessary to cover the plan.
I also installed a couple of games I thought I'd enjoy during the 4th of July weekend promotion where they were giving 3x rewards for offers, and have gotten a little over 500 coins by playing those games instead of doing other stuff for fun. One of them I actually enjoyed enough that I put a dollar into its in-app purchase for a perk that made it more fun, but that hasn't affected how many coins I got from it yet (I think it makes it slightly more likely that I'll hit one more milestone before the timer on it runs out).
Anyhow, the math is:
5 coins for daily check-in, 50 coins for mostly ignoring 25 videos, and minimum 5 coins for a spin is 60 coins per day. 7 of those in a row also gets two 75-coin streak bonuses for a total of 570 coins per week. Three such weeks, including the successful streak completions, is 1710 coins. Taxes and fees may vary by location, but for me they're about a buck, so that more than covers the bill. In fact, 23 ads a day would still cover it in three weeks, and averaging 13 a day (edit: I said 8 at first, not sure where I messed up my math) would cover it in four, even with all minimum spins. So as the others have said: until they start making points harder to come by, if you have the luxury of a regular enough schedule of applicable time, it's absolutely possible. But it certainly isn't for everyone, and there's no telling how long they'll keep the program going.