Let's say we have a single mom with three kids (aged 6 to 8), who all want bikes. Our mom loves her kids, but she also has to be frugal.
She doesn't think it's smart to get them brand-new bikes as the kids will outgrow them in a year or so. Plus, they might not like riding at all when they try it.
So she might go for basic used bikes at first. When her oldest is a teen, he'll get a brand-spanking bike with all the bells and whistles. It'll hopefully last him for years.
What would be an idiomatic way to describe the mom's reasoning? (The shorter, the better.)
As in, "I'm not getting all of them new bikes, it's not a worthwhile investment". Or: "Now that Mark is 13, he can get a fancy new bike. It's a worthwhile investment now".
(Example sentences are just guidelines, totally malleable.)
Edit #1: A single word would work too.
Edit #2: I'm trying to specifically emphasize two aspects here: (A) the timely/untimely nature of the possible investment and (B) the cost-to-benefit ratio associated with it.
Edit #3: I'm looking for a common idiom, something the mom would use in everyday speech.