Even if it's not to scale (heck, what really is in most toy lines anyway)
BBI and X-Treme Detail for starters... Both of which make incredibly complex vehicles out of more parts than probably 10 Hasbro toys combined and for prices that rival Hasbro. I've never seen Hasbro as having an "excuse" with vehicles, and the way they factor size and price they actually don't make an excuse either.
A ship is often scaled to the packaging more than the figures... price maintains at a constant ($15, $20, & $30 if we're using ROTS as an example). The ship is made to fit a "standard" they've set for the box though... Could they deliver more? Sure, but it would require deviating from presets which they won't do... If it's to-scale by coincidence though it works, like the Tri-Fighter, JSF's, etc...
Thankfully they get off their ass now and then and do something pretty spectacular though like the TIE Fighter last year or the Saga Landspeeder. I only hope things like AT-ST, Snowspeeder, and some others get redone... Otherwise I've come to expect little out of them with their vehicles.
When you open a $20 halftrack from 21st Cent. Toys and compare it to anything Hasbro made though, there's simply nothing they have that has come close to that quality level... No matter how big or small the Hasbro ship is.
For me, ships are so collector-focused these days anyway (honestly, look at the exclusives... Unless its a movie year, ships generally go to the adults) and sell so poorly overall (I blame a bit of burnout on the "same old same old" here) I think they'd be better off doing less and less vehicles within any year and they should focus producing all-new and "collector-focused" ships every whipstitch as exclusives (like the Landspeeder)... Preferably ones that can be repainted and re-released as something totally new ala what the military lines do to help the costs.