Ya, looking online they list wild-param's usually that the fish come from but doesn't mean that's what they can do fine. I've had my platys in 3 different tanks now from pH 6, gH 4, to pH 7.6, gH 9 and they are still breeding like nothing changed. Also, just plopped and dropped them too when I moved them from tanks.
Yes, it's an expensive hobby. That's why most of us start getting plants, shrimp, fish, something we can sell at some point and make a few bucks back or enough to upgrade or keep the hobby going. I'm almost out of prime, flourish, excel and RO remineralizer, not a bill I'm looking forward to getting from the LFS, and of course I can't go in there without wanting something else.
What you have is officially called MTS. Multiple Tank Syndrome. I started out with a few turtles and got a 39gal. Tank was too small, got a 55gal. They become aggressive with each other, used the 39gal and the 55gal. Wanted some fish, got a 10gal. Got some plants and shrimp. Got a 2.5gal for my GF who wanted a betta. It goes on but I now have the 10tanks in my sig in just over a year. Luckily, a lot of the plants I've gotten cheap, for free with shrimp purchases or just waited it out and propagated my own plants. Shrimp, started with a few of each breed and been patiently waiting for them increase the population.