1GB ram devices = 380MB ram usable for running app.
https://msdn.microsoft.com/en-us/library/windows/apps/jj681682(v=vs.105).aspx
Incase you don't know how tumblr work, when you using tumblr app, your phone will keep downloading image everytime you scrolling.
It just simple math, my internet speed is 3MB/s (25Mbps), so it only took 1 minute and 40 seconds to fill up all 300MB RAM available (80MB for the app) while I'm using the app, now CPU have to process and releasing RAM to make space for the newer data every 1'30", while CPU processing all the image and UI to display => higher CPU usage.
Unless you have the phone with better CPU or more RAM, then too bad in this situation.
I'm aware that a 1GB WP device caps an app's memory usage to 380 MB. It doesn't matter. Even with half that amount, the idea that an app couldn't display a list of 2MB images makes no sense. I've done it myself. While the math you've presented isn't wrong, it's in no way an accurate representation of what WP (or any other OS for that matter) does under the hood, neither in terms of memory management nor in terms of how the CPU factors into all this. However, I don't want to argue over why none of that really makes sense. I'd rather just focus on what your tinder developer might do in this particular situation. Here's one approach (there are more):
a) monitor when the list with images is being scrolled very slowly (or not at all) and determine which low-resolution images are on screen at that time
b) load into memory the corresponding high-resolution equivalents
c) fade-in the high-resolution equivalents ontop of their low-resolution equivalents.
d) unload the high-resolution images as soon as they are scrolled off screen
If done right, the casual user won't notice what's going on. The user will just enjoy the higher quality images and eventually take it for granted. There'd be a lot more to say about what your tinder developer is likely doing and how this would all work, but it doesn't make sense to get into all the gritty technical details here.
If this still doesn't convince you, then consider that Android also caps the memory that is made available to an app. This cap can vary widely from one device to the next, and isn't directly connected to the device's RAM capacity like it is on WP. In affect, a 2GB Android device can (and in some situations will) limit an app to less than the 380MB that it would get on a 1GB WP device. My point is that
devs deal with the exact same problem on Android. Adding more RAM to an Android device doesn't magically solve this problem any more than it does on a WP device. Both are affected by memory caps and both must deal with having less memory than is desirable without sacrificing quality. Maybe your tinder dev knows his way around Android but is a WP newbie? Certainly possible...
Except every developer willing to developt app for iPhone and Android, and they're willing to optimized for the iPhone rather than Android. Are you sure that they will take their time to optimized for WP10 app?
The differences you're noticing in memory usage has, in almost all cases, absolutely nothing to do with how iOS or Android developers do or don't optimize their apps. The differences in memory usage on iOS and Android are primarily a function of the OSes themselves. This revolves around runtime environments (Android has one, iOS doesn't), memory garbage collectors (Android uses one, iOS doesn't) and a few dozen other things that have nothing to do with developer's willingness to optimize.
The same applies to memory management on WP. Ignoring bugs and the occasional outliers, where some devs really can be exceptionally good or bad at their craft, most differences in memory usage will come down to differences between OSes, not developer "optimizations".
The point is, I want 1GB should be smooth and enough for WP, and now MS are willing to go after Android which is need more RAM to be better perfomance.
Oh and I heard from somewhere, Windows 10 will have the VM to run the ported apps from Android, that's why 1GB ram minimum is required and 940 may have 3GB ram.
All the FUD currently being spread on these forums in regard to how Android apps will run on WP (will it require a VM? Can devs upload their APK? etc) is exactly that. BS. I've yet to see a whitepaper detailing any of this. It's all premature speculation. And again... for the gazillionth time (in general on this forum, not directed at you)... stop worrying about Android apps on WP. Like I said, that's not what people will be porting to WP.
95% of the time it's the iOS apps that we'll be getting, so this stink about the overhead of Android apps on WP is somewhat pointless.
Don't get me wrong. I'm not against WP devices generally shipping with 1GB or more. I'm just pointing out that yours are not the best reasons for doing that.