I'm not very familiar with the business model though, especially with regards to businesses that don't sell bagels but make software, or sell services.
Bonuses, retirement plans, health benefits, and all other incentives are still set at management's discretion, but are funded with the other 70% of the profit. It's really that simple.
Realize too, that simple profit sharing coexists with the normal grading of wages based on whatever position/seniority algorithm the organization uses. So you're guaranteed, as a developer or designer or whatever, to make your normal wage and be considered for increases. But every pay period would have that profit sharing bonus that shows you how the business is doing and exactly how much your organization values your contribution.
Stock-based incentives are supposed to fulfill this role, but they're often given out after some major event and then only to the most visible members of the contribution. Arbitrarily, in other words. Holiday bonuses are nice, too, but they are supposed to be confidential in most organizations (creating uncomfortable speculation and comparisons) and can lead to unmet expectations.