Incorporation of California Non-profit Corporations, including filing of IRS Form 1023 or Form 1024 application for 501(c)(3) (to provide for tax deductibility of donations to the charity made by donors), 501(c)(4), 501(c)(6), 509(a)(2), etc. federal tax exemption, plus state exemption application, if applicable -- are generally $2,500 and up, plus costs, for a full service flat-fee package. These fees represent discounted rates that are disproportionately small in comparison to the amount of legal work and attorney time typically required to establish a non-profit organization. The legal fees are thus already discounted from for-profit legal business setup fees as a public service and no further discounts on account of non-profit or tax-exempt status can be made. Please keep in mind that, regardless of how worthy your cause may be, it may not be "my" cause.
Non-profit corporations where no tax exemption filings or related advice are required typically follow the same fee schedule as for-profit incorporations (that is, $1,500 and up).
Costs / filing fees inclusive of tax exemption application filing(s) depend on the nature of the non-profit, but generally range from several hundred to several thousand dollars. Costs average around $1,000; any firm or service that lists costs at of a couple of hundred dollars or less is counting on you to make your own tax exemption filings (and, probably, to figure out which filing(s) are needed, how to properly complete and prosecute them, and whether you need to make them at all, as well), so be sure you are comparing apples to apples when choosing a legal services provider.
Where rush processing is required, additional fees and costs will apply, so plan ahead and start early if you can.
Filing of IRS Form 1023/1024 and/or California state exemption applications without incorporation services, or for not-for-profits that are not organized as corporations, is also available; standard flat rate for most such situations is $1,250, plus costs.
If these fees and costs are a barrier for your nonprofit, my recommendation is to consider the following: (a) Is the charity really needed? Is there an existing charity you can volunteer with, meeting the same needs in your community? (b) Are there other founders you can collaborate with? Split three or five ways, the startup costs may not seem as onerous, and may additionally be tax deductible as contributions to the charity.
Once formed, and for existing non-profits, if tax-exempt, these organizations qualify for my lowest hourly rate of $350.