So, in this particular case, each tab ate about 50MB of RAM. You started with no other apps running, Safari is the only one running. Now, imagine you have other apps running and they use 300MB, you have less than 200MB free, you launch Safari and open these 4 tabs. Now you're in memory starvation situation and tabs will be reloading every time you switch between them.
Is Safari the only app you ever run on your iPad? If yes, then loading 4 tabs without recurring reload is possible, but your usage case is a tiny minority of how most people use their devices.
I had at least two other apps running (the system manager and App Store) .... But if you want to use safari with 4 tabs opened and 3-4 heavy apps running in background, well, the one with ridiculous expectations are you.
This is A TABLET, not a MacBook Pro ....
There is an app manager, close your apps (or keep alive only the one related to the contents you are browsing, if any), browse safari and when you need re-open the apps.
You are trying hard to demonstrates that the iPad is underpowered, but with the same philosophy I can do the same with a MacPro and 16 Gb of ram: just keep open apps until I saturate the available resources.
This is a tablet, use it as a tablet.
Don't get confused by android tablets pumping specs at every release: they are trying hard to catch up and Samsung approach at the matter is well known.
You have 1 Gb ? We'll going for 3 Gb !
You have a dual core ? We'll use an eight core !
And so on ....
I'd like to have 2 Gb in the next iPad, but just for future, more complex apps. Not just to keep 7 tabs and 5 apps opened at the same time, while I can barely use one.