If you really want an open bed, the pickup configuration of any fiat ducato, toyota dyna, mercedes vito or sprinter, etc., will work and have much more space. All 3 sides fold down, and you can even get power tilt or a small crane if you want. The dyna is like a scaled up kei-car.
There's plenty of variation as they're all custom, and as they are work vehicles there should be plenty of cheap used ones on the market. The bed is also just a plate bolted to a steel frame so you can do whatever you want with it easily - adding custom boxes underneath, built-in ramps, changing the floor, whatever. They're also available with tall roofs with openable soft cover.
But as others suggest, used closed vans are also cheap and quite spacious, and on the big end you have the usual choice of a long-body sprinter which could probably fit 3 motorcycles inside with space to spare, with a much lower ramp height needed to get them in/out. Look around - it might not be as sexy, but there's definitely something that fits your need.
There's plenty of variation as they're all custom, and as they are work vehicles there should be plenty of cheap used ones on the market. The bed is also just a plate bolted to a steel frame so you can do whatever you want with it easily - adding custom boxes underneath, built-in ramps, changing the floor, whatever. They're also available with tall roofs with openable soft cover.
But as others suggest, used closed vans are also cheap and quite spacious, and on the big end you have the usual choice of a long-body sprinter which could probably fit 3 motorcycles inside with space to spare, with a much lower ramp height needed to get them in/out. Look around - it might not be as sexy, but there's definitely something that fits your need.