Assess the Wiring
Often the biggest factor affecting the cost of recessed light fixtures is how much new wiring is needed. If you're replacing existing lights with recessed fixtures, chances are you can use the same circuit to supply the new fixtures, and the electrical work may be minimal. On the other hand, if no fixtures or suitable circuits are in the area, you'll need to tie into the closest appropriate circuit or install an entirely new circuit and breaker; this isn't a huge deal, but it can easily add $100 to $200 or more to the project cost. Have an electrician come over for a quick assessment of your plans. Many will do this for free on the prospect of getting to bid on the job.