The technology to do asymmetric upload/download exists and many fiber-based companies offer it at the same rate as older infrastructure. It is not more expensive to offer symmetric service, but it may require infrastructure being brought more modern.

For example, in the same region of Massachusetts (around Worcester) I previously paid $40/mo for 300/300 Mbps to Verizon FIOS but now after moving I pay $40/mo to Spectrum for 500/15 Mbps.