How would I react to being told I need a new bass at £2.5k? I'd laugh it off and say I have good enough basses thanks, you worry about your own gear.
If I was discussing gear and a band mate said "mate, you need fanned frets, a dark glass pre-amp..." and a very specific list of stuff they think a bass player should have. I'd probably just think they're a gear obsessive and next week it will be all about Moolon P basses with flatwound strings that have been washed up on Skegness beach. The week after it will all be Wishbass, OK maybe not those, custom made coffee table basses... And so it goes on. Tell him no guitarist ever sounded good without a 50s Tele. A real one, from the 50s. Through a genuine original Fender Bassman amp with a serial number starting....
You want to upgrade your bass. You like the idea of a Jazz 5 and a Ray 5. Get what you want to play, it's your cash, your instrument and something you have to live with. This band could go under any second and you could be left holding an instrument worth 2.5k that just one of that band recommended to you once. A Sterling Ray 5 covers fractions of that. They may have been forceful in recommending it, some people are like that. And it's easy spending someone else's money.