The pricing of Philadelphia's bikeshare program is pretty weird.
One ride? A whopping $4.50 for 30 minutes; extra $0.30/min if you go over or use electric. Bus fare here is $2.50 and gets you free transfers.
Day pass? $15, getting you 60 minute rides, and $0.20/min extras. It would make sense if you planned 4 rides in a day, or wanted longer rides where you didn't reach a dock in 30 minutes. (Though for the previous plan, one 60 minute ride would be 4.5 + 30*0.30 = 13.50.)
Month pass? $20, basically like having a day pass all month. If a tourist makes 4 trips over two days it doesn't quite break even over single-rides, but 5 trips would. And a month pass is much cheaper than two day passes.
Next tier bills you for the whole year, at what amounts to $13/month; same benefits. Apparently it's worth a lot to the system to lock you in. It occurs to me that given Philadelphia weather, someone doing a monthly plan might cancel in the winter, figuring they wouldn't use it then. With a 35% discount that becomes less complelling, and if you have the annual pass you're more likely to use it on good winter days.
The final tier also bills you for the whole year, at just under the $20/month rate of monthly passes, and gets you a new benefit: 2 free 30-minute ebike rides daily. I'd guess it's aimed largely at commuters or students: ride to work/school each weekday, and maybe futz around on weekends too. And if you know you're going to be around for a year, and were thinking of the monthly passes... it saves a few dollars to get this final tier instead, and the free e-bike rides.
Note that a paid e-bike ride is a whopping 30*0.20 = $6 for 30 minutes, so even just one such ride a month will incline you to go from the $13/month regular annual tier to this $19/month final tier.
Basically the system really soaks any tourists or visitors or people wanting to just try the bikes a bit, and drives you toward making a deep commitment with a modest level of regular e-bike use.
The actual system seems to have a lot more e-bikes than classic now, so either a lot of people are using that free-ride tier, or people are paying a lot of money for e-bike rides.