[benjamincburns]

That's not a terrible idea, actually.

When you purchase any NAND flash device like a USB stick or an SSD, essentially the same thing is happening. The raw storage is much higher, but due to a high raw bit error rate (see NAND displacement errors), the need for wear leveling, and the need for reserve blocks to swap into service as the device ages, the claimed capacities are reduced to accommodate MTBF and observed bit error specs.

In cases such as this I think it'd be disingenuous not to drop your claimed specs to reflect the actual usefulness of the device.