You're both right.
Brentford built up their budget from selling players for eight figure sums and buying cheaply. But at the same time, they used the "Moneyball" method to identify the players they needed to push themselves on. An example is Nico Yennaris (or Li Ke as he is known now that he plays for China). They bought him off Arsenal for relative pittance; he was never going to make the breakthrough for Arsenal and was even mentioned as being "too lightweight" for Brentford's first team. But, he had one of the highest tackling success rates in the U23s league, so when they finally got him going after an injury hit start, he flew in that position and was purchased by Beijing a couple of years ago for a decent fee.
For Brentford, it didn't happen overnight and chairman Matthew Benham was hardly a billionaire. Once they got promoted, they didn't change their model and kept persevering, until they had built a squad that was both gelled and full of quality.
We need to be doing something similar. If we can sell players on for ten times what we buy them for and steadily use that money to build a squad capable of challenging, we'll be golden.
The current methodology around scouting is constantly changing, some use programs, others prefer trusted scout reports to identify players they want. Some even use Football Manager's database (looking at you, Everton and Wimbledon). LD didn't shake things up when he came in, I didn't rate him at first but he's quietly gone about his business and has picked us up some decent players. I still think we could be a little more meticulous in how we look at players, but I'm not going to criticise a set up that's kept us up this season for peanuts.