The difficult step is the first genome of any organism. Once you have that, the next one can be assembled using it as a template. A new genome requires much more sequencing to get a good assembly.
The cost and complexity is driven by the end purpose. The inexpensive methods Darrel refers to are good for finding markers but not so good for putting a brand new genome together, which is still a bit laborious.
De novo genome assembly: what every biologist should know
You think GM plants are controversial, wait until we have $100 genome technology available.