I agree with this. That's why I've been arguing so strenuously to acquire FA for money only and to spend every penny that we can internationally to put more quality prospects on the farm. You really can't afford not to have a constant flow of prospects to the major leagues who are good enough to be regulars. They are the cheap salaries who balance off the big contracts. The Phillies problem circa 2010-12 wasn't that they had big contracts of guys who would decline before the contract expired. Every team had that. The problem was that as holes needed to be filled, there were no young players to fill them, so the Phillies had to keep going the FA route (or trade for a contract, which cost almost as many $, but also further defeated the farm). Whether a Pence is a 'reasonable contract' or not, he's way more expensive than an OF who's a rookie or in his initial 4 seasons. In modern baseball, a team can only remain good for an extended time and manage the salary cap with a constant flow of young talent. That also means, if you have a home-grown team of popular stars who are growing old together, you have to bite the bullet and gradually trade one or two of them at positions where you have plausible young talent coming up. If you trade from the farm too much or don't keep feeding the farm, there is no plausible infill talent and you either age out as a team and face the major rebuild that the Phillies do, or you keep patching and filling as the Phillies also did and watch your salaries climb above the lux tax threshold.
Btw, that's also the argument against your plan to build a wave of young talent good enough to win 85 games, before signing FA: 1)your talent is too much the same age and grows old and expensive together -- a team that wins a lot can ruthlessly weed them out and replace them with younger at the right time, the fans of a team like the Phillies who make infrequent trips to the WS is too nostalgic about their winners to permit that and 2) you are buying FAs at a time when your payroll is poised to explode. We now have 4 years of grace on our payroll. Apart from Nola and Odubel, nobody requires big money in that time frame. With the wave of young talent you see coming, we can afford to carry 5 guys making $25 million a season and be comfortably below the lux cap, so there is money for filling an emergency hole. And no, with the flow of pitching talent, it we don't trade it away for $ 'cheaper' talent, there is no need to spend big $ on relievers. We grow our own and fill in with cheap from outside.
That is the modern model for baseball success, and even the Yankees are going that way: 5-6 expensive stars (home-grown re-upped, traded-for expensive vet, or FA, in balancing the budget it really doesn't matter -- both are auction priced) surrounded by cheap, young, home-grown from a well-fed farm. Because the Yankees are willing to spend two-thirds of the years above salary cap, they can afford one more established star than we can.