Outposts is certainly not a cheap solution, a dev rack with one m5.24xl is $124K, a similarly configured Dell server (but without the rack or AWS management) is less than half that price.
https://aws.amazon.com/outposts/rack/pricing/
I didn't calculate to see if the bigger racks are more cost effective, but I'm guessing not if 5 m5.24xlarge, 4 c5.24xlarge, 3 r5.24xlarge costs $690K.