Quoted from singapore_pin:
In theory yes, however freight forwarders have many customers that want to ship single items, few boxes etc. They put all the cargo in a single shared container and charge the customers accordingly
That's called LCL shipping ... The shippers sell the space by the cubic metre. Cheaper than air freight by half, generally. But a lot slower, of course.
Shipping a whole container is surprisingly cheap on a per unit basis. A whole 40ft is probably $2000 USD from Rotterdam to Chicago, divide that by 40 units and it's only $50 per machine port to port.
(I used to ship 100x 40ft high cubes to NZ a year ex Shanghai in my previous life ... From memory they were $2400 USD plus charges per container, took 21 days to arrive)