Yeah, if the price is too good to be true, it generally is... 128gb Sandisk was bought from Amazon.com. It works fine and is genuine. Was $120AUD. That's less than a dollar a Gb...
Don't buy generic from ebay, it will read as 128gb but in actuality will be, if you're lucky, 8gb or less... Once you get to the sd cards capacity it just fills in empty files. Looks like it's there and works while in PC but as soon as you insert in tab or phone it has nothing but corrupted sectors.
Most of the sellers of these are fly by night cowboys who have been members for less than a month. And there are multiple accounts all about the same price but by different members...
You have been warned...
Here's a readout from an app that tests a card - I only did a test on 30gb as that should tell me. Name of app is at the end...
Warning: Only 30000 of 243991 MByte tested.
The media is likely to be defective.
0 KByte OK (0 sectors)
29.2 GByte DATA LOST (61440000 sectors)
Details:0 KByte overwritten (0 sectors)
0 KByte slightly changed (< 8 bit/sector, 0 sectors)
29.2 GByte corrupted (61440000 sectors)
0 KByte aliased memory (0 sectors)
First error at offset: 0x0000000000000000
H2testw version 1.3
Writing speed: 13.1 MByte/s
Reading speed: 13.5 MByte/s
If You Disagree Or Think I'm Wrong, Look Closer At My Avatar...