This is not true. Trickle down economics is the theory that money given to rich people will enrich poor people because the rich people will use the money to buy goods and services the production of which will require the labor of poor people. That is, this extra money at the disposal of rich people will create an economic domino effect such that money will ultimately end up at the disposal of poor people. In a trivial sense this is true. The theory is only interesting if this is an efficient way to increase economic activity generally without deleterious side effects.
But it never was the theory that giving money to rich people would spur research and development such that services ultimately were cheaper.
As to whether it's a scam, that is another matter. The allegation then is that the boosters of trickle down economics do not believe their own claims as to the efficiency of this process. That is, they believe, because it is tautologically true, that this will enrich those who are already rich, and they desire this, and the story about the efficiency of this process is a tall tale to salve consciences or win over rubes.
"[I]f the income share of the top 20 percent (the rich) increases, then GDP growth actually declines over the medium term, suggesting that the benefits do not trickle down. In contrast, an increase in the income share of the bottom 20 percent (the poor) is associated with higher GDP growth. [1]"
[1] https://www.imf.org/en/Publications/Staff-Discussion-Notes/I...