"Expensive guv.
It's not just a matter of cutting a hole in the floor you see.
There are power lines to re-route, water and air pipework to shift. Then there is the matter of cutting through the bulkhead.
Nah, not cheap.
Then there is the recalibration of the floor grav plates and acceleration compensators, you also have the choice of hatch or iris valve, ladder or elevator.
Call it a hundred thousand and we can get started Tuesday."
My advice - get your ship engineer to cut a hole in the floor, make a ladder and fit a hatch from the scrapyard - a few thousand at the most.