To a degree, the motorcycle comparison is apt: You could step up from a Yamaha R3, which you ride well, to a full-tilt Yamaha R-1M, it's only money. However, when you sit on the R-1M, thumb the starter and head out around Watkins Glen, you do NOT automatically become Valentino Rossi.
Great players have built entire careers, famously, playing only a Precision Bass.
It's all down to what you prefer, what inspires you to reach out, learn more, or just what sounds best to your ears. It's that simple. For some guys it's very expensive basses with complex amp and effects rig. Then just as many as a bass, a cable, and an amp.
You might at some time be moved to investigate a two pickup bass. Or a neck through. Or any other number of choices. On the other hand, you may very well be in your 'happy spot'.
I've owned everything from Peaveys to Alembics to Squiers. Each provoked some different tones, might have influenced me to play certain things differently, had different levels of pride in ownership. But out of these many, I can tell you that no particular one was the Rosetta Stone that unlocked some mystic secret to it all. They were all different flavors or takes on a certain tone or construction that added to a knowledge base from the experience of them all. And for me, I always sounded like me. Granted it may have been a better-sounding me on the Alembics, but none of them were a night and day revelation.
We play what suits us best, whatever that may be, and it's different for each of us. I'd say you've saved a fortune alongside your very fickle guitar player: He THINKS it's the guitar . . . . and not him.
Don't get me wrong: More than a few guys legitimately feel they need THIS bass for THAT sound, and then this other bass for this other tone, and like guitar players may carry several for different situations, and that's their thing, and it works for them.
I always felt it had to start with me. . . .than a different instrument, which doesn't really work for me. Others CERTAINLY have a different outlook and result.