Looking for high bandwidth rooftop to rooftop solution ideas

Edit: Fixed Gbps, not Mbps.

One of my clients is expanding into a building within the same office complex but not directly next door.

They have a need for large data transfers between buildings. They expect to be generating about 60 GB of data daily in one building that needs to make it over to the other building.

I initially looked at some rooftop 24GHz solutions but was seeing max throughput of about 1.45 Gbps (correction from earlier). I then suggested that we trench fiber between buildings and handle the delivery that way. With fiber, I can run multiple 1Gbps or 10Gbps links and data transfer wouldn’t be a problem.

The contractor gave a quote for the trench and now the client is having a bit of sticker shock.

Are there alternative rooftop solutions that I’m not finding that offer higher bandwidth? RF or optical?

Can multiple RF pairs be “stacked” to form a higher bandwidth link?

My alternatives are to have higher bandwidth ISP drops and do a VPN, look at MPLS (assuming ISP supports it) instead of the VPN, or look to drop servers in the new building to capture data and the stream it out slowly.

Any advice would be great!