I keep the species separate in my stacks as much as is practical. I do have one mixed rack right now, but the rest of my stacks are all oak or all ash at the moment. I do it partly because some species season faster than others, but mostly because it just appeals to my sense of organization.
Mixed loads $200 cord, all good hardwoods, some ash,oak,sugar,locust,black birch etc...straight oak is $250, for smoking, one place uses 30" green black birch and sassafras ,About two to one, I cut a load for every Thursday by noon when they start smoking, if I take a week off I just bring two loads, if they have enough for their smoking session that week they will call me Friday evening. I provide 1/4 cord a load at $75, so $300 cord. Another place wants all barkless oak, split real small, for cooking pits, smoking. That goes for $350 a cord, I made a 12 way wedge with 3 rings as well, think of as rings on a bullseye, makes short work of that order. Third place uses small split maple for cooking, at $250 cord, and black birch "pie pans" for adding smoke. I charge them $300 a cord.
Lots of repeat customers, I tell all new customers I only cut for orders a year ahead, than they gawk at my price, kinda high...than in January or February they call asking I I have , and last week or two's cut and split ash, dead from borer, goes for $225 a cord, than everybody and their brother who needs wood yesterday will call me. I never understand it....