I think a lot depends on who your clients are and what your business is. If you're talking about a real professional services engagement (Accenture, Oracle Consulting, whatever) then $300+/hour for an architect-level resource is pretty standard. Hell, junior business analysts get charged out at $175/hour.

As a one-person shop the value you can bring is probably lower because you don't have the synergies of a team and you will have to spend some of your time doing junior BA-type work. You can't charge yourself out at the full rate of an architect-level resource because you're not spending all your time doing architect-level work. However as a one-person shop your overhead should be lower (e.g. no HR people or other cost centers to support with your billings).

$75/hour seems awful low as a 1099/consultant, so it's no wonder businesses are happy to pay that.

IEEE consultant surveys indicated ~$150/hr for a well trained consultant in software is median last time I checked. But what you get depends on how you get your business and what your approach is to selling your services.

I think I'd find it impossible to charge more than $200/hr for embedded firmware (Boston), but could probably get $400/hr for systems engineering or industrial design to develop an integrated complex solution to a business problem that they don't have the in-house expertise to deal with.