Or we need to bite the bullet and build a HLLV system.
Launching from Earth into space is expensive, and that's just the way it is. We need a 100-200 ton launcher to build up infrastructure in space so that the need for resupply from Earth becomes an occasional thing. Thermal and electric rockets (NTRs NEPs) need to be developed which can run on a wide range of fuels, and with no need for cryonically stored oxygen. Simply heat whatever gas is handy into high thrust steam.