Which is why flash remains much more expensive than HDDs.

Flash is also much faster than a bubble memory, because it provides random access to blocks, even if a block is read sequentially. Thus flash was positioned in a good spot in a hierarchy of memories where a compromise is made between access speed and cost per bit.

To achieve a similar speed, a bubble memory would have to store a block, e.g. 4 kB, per bubble ring and have a huge number of bubble rings (i.e. billions, to compete with the current flash memories) to which random access would have to be provided by semiconductor ICs handling the multiplexing and demultiplexing of data.

Due to mixing ferromagnetic and semiconductor technologies, it is very unlikely that such a device could be made at an acceptable price.