I don't have any salaried employees, but I've worked both sides of the full-time/contract for services coin.
The general rule of thumb for contract vs. full time with all benefits for professional services seems to be that you take what you'd make on salary, convert to an hourly rate (assuming 40-45hr/wk) and roughly double it, then round down to the next "nice" hourly rate (usually a multiple of $5). This varies a lot with market, the kind of benefits you're comparing with on salary, etc.
A good "freelance" rate might be $45-50/hr to end up comparable to a 50k salary with full benefits (group health insurance, PTO, "other half" of FICA, etc.). This not only reflects the additional expenses the freelancer incurs but also puts a small premium on the services due to the supposed lesser certainty as compared to a full time hire (though people hire/fire so quickly these days that may or may not be totally relevant, anymore) which would encourage a full time hire and the corresponding "steady paycheck" if they actually want full time.
This also corresponds to what it would cost for a company with several full time employees to provide similar services on a contract basis. They obviously have to pay their employees, including all benefits, and then they still want a little profit on top of that. A company with lots of resources ("highly paid consultants") will want more, but they'll also probably bring some real resources (equipment, vast past experience, etc.) to the table that you can't match as a freelancer.
Obviously this will vary somewhat by region and with the labor/services market in your area.