Online Fabrication Services
The following list are online fabrication vendors.  Last we checked, they are still open for business.  Most of these services can quote a price before any work is done.

Online Laser Cutting Services
Big Blue Saw
Ponoko
Send Cut Send (metal laser cutting only)

Online CNC Services
eMachine Shop
3D Hubs
Xometry
Protolabs 

3D Printing Services
Shapeways
eMachine Shop
3D Hubs

PCB Manufacturing Services
OSHPark
Advance Circuits

Waterjet Cutting Services
Big Blue Saw

 

Quote Process

Some of these services have instant quoting.  Export your CAD drawings in a format that the service requires, pick your material, and your quantity.  The more you want, the cheaper each individual part will be.

I went through the process for a small aluminum part.  The quotes can be seen below for CNCs, waterjet cutting, and metal laser cutting.