I think reasonable thing here would also allow contractors send counter offer. Maybe 10x 100x or 1000x. Then it would be up to side ordering to accept or reject one of those.
And if the company makes it a policy to never accept any counteroffer (which is legal and fair), you're back to the same system, without that feature existing.
Platforms sometimes care—by which I mean, achieve a market position that means sellers can’t afford not to use them, then leverage that power to force lots and lots of weaker people and entities to do what they want, possibly causing higher lowest-prices in the overall market in the process, so, also hurting buyers.
