Handling cinematic spaceship fights and other sci-fi stuff

[TerryW]

Small spaceships have costs comparable to cars and mopeds while the larger ones are basically boats as far as price goes.

That's definitely not GURPS Spaceships, unless you apply a lot of houserules.

You can get cheap ships with Spaceships rules, assuming you buy them used and worn out, but it's used light aircraft cheap not used car cheap. It also sounds like you want your ships to do some fairly unconventional things (By GURPS Spaceships standards) so you'd need the first PDF plus at least Spaceships 4 and 7.

If you're comfortable with just eyeballing the stats for your ships, and your players are having fun with that, I don't see a lot of need for Spaceships.