Action speaks louder than word. Can't prove anything while running around naked.
I got a suggestion for you: Make a character that can steamroll mp10 with the LEAST amount of money possible. Keep a record and show it off here. That will prove whether or not your reputation is legit.
You also need that as your showcase, if you want people to use your service.
but with only 1.3 bil, you can only get 2-3 good pieces these days. everytime I see something I like, price is always 500 mil+ minimum.
Like with most things the sum is larger than the whole. If someone wants a 500m barb I'm not going to buy them 1 items worth 400m + 12 worth 100m total. Just because people have 500m items doesn't mean their build is better than a 200m build.
From my experience there's a significant asymptotic curve happening after 300m builds so there's no reason to go higher imo.