128gb stick with very low write speed doesn't make any sense to be honest...

If you are using a memory stick to make a backup copy of something then the speed isn't important. Computers can do more than one thing at a time, you set your copy going and leave it to do its thing while you carry on doing whatever you usually do on your computer. Come back to it a couple of hours later when it is done and put it in a safe place hoping you will never need it again.

Except for, say, archiving, etc.

So it's increased in price by £1 since I bought one last September.

128gb stick with very low write speed doesn't make any sense to be honest...

got one of these, loads of series plugged in android box.

How long do you think it would take to transfer say 100 GB onto this drive?

If you are using a memory stick to make a backup copy of something then the speed isn't important. Computers can do more than one thing at a time, you set your copy going and leave it to do its thing while you carry on doing whatever you usually do on your computer. Come back to it a couple of hours later when it is done and put it in a safe place hoping you will never need it again.

USB 2.0, to slow for 128gb

Well if I was I wouldn't sit there watching it - you would be some sort of plank to suddenly decide "I must go and copy 100gb of files to that USB drive".
Everyone wants the best, biggest, fastest, but also want it cheap.

will take 35 hours at maximum theoretical speed to fill this up. assuming you lose 20% overhead this will be 42 hours.