In another thread, I suggested an eMMC slot same as what Pine64 uses. This is a connector on the main board to allow a small, (postage stamp sized), daughter board with the eMMC chip on it to be installed.
This would allow the user to either choose SD card as the cheapest option. Or buy an optional eMMC card, (of various sizes).
In the case of Pine64, they make 16, 32, 64 & 128GB eMMC boards. The larger ones are not cheap, yet still reasonable given their size, speed and reliability. Their is nothing stopping Beagle, or another vendor, from making a 4 or 8GB board, which would be cheaper.
Samsung even makes a 256GB eMMC chip, though no one I know makes it into a Pine64 compatible daughter board.