The cost of that trade in terms of salary cap and cash:
Pick 6 - $7,742,361 2026 salary cap, $42,582,984 total cash
Pick 39 - $2,275,957 2026 salary cap, $12,517,762 total cash
Pick 12 - $4,817,044 salary cap, $26,493,742 total cash
Pick 20 - $ salary cap, $21,090,674 total cash
So overall the trade also saves the Browns $1,366,606 of salary cap space this year and $7,516,330 of cash over four years. You don't make the trade to save money but it is an added benefit to spend more on extensions, free agents and other trades.
Having three top 24 picks give the Cleveland Browns more chances to add offensive talent to the team, they can add an offensive tackle, wide receiver and one extra move. The third first rounder makes taking a gamble on a quarterback easier if that is their chosen direction too.
The other option is to trade out of either pick 20 and 24 to collect more assets.