I've personally gone both routes with this mod on two different F-150's. Option 1, upgrade gears on existing axles and option 2 source axles from salvage yards with desired gears and do the installation myself.
Regearing stock axles at a competent shop was $1,650.00 back in 2020
Sourcing a 9.75 from salvage yard was $500.00 back in 2022. I did the install
Sourcing a 8.8 front diff from ebay was $280.00 back in 2022. I did the install
You can definitely save money, but you have to be mechanically inclined and have the tools to do so.
