Well, I don't own one (although I'd love to have my own doggie stuff store) but my trainer does and I take Loki at least once a week. It's about $20-25 in this area. She has a few loyal people like me who understand how much the dogs need it, but I encounter a LOT of people who are unwilling to spend the money. She does some pick up and drop off and people sometimes do a split day with the local groomer so their dog doesn't have to be crated at the groomers all day. We probably have 5 dog daycares within 15 miles around here, but this is the only one I'd ever take Loki to because the trainer runs it.
We also have a local "petsitter" and she does it full time. It's about $15 for a 20 min walk. So daycare is not much more for the full day. But if you think about it, the daycare is going to have significantly more overhead. So unless you are planning to run a training facility as well, you might be better off with the dog walking service.
On the other hand... I pay $20+ once a week so that I DON'T have to walk Loki in the cold weather, or hot weather, or rain....

We love to walk, but not unless it's 50-70 degrees and sunny!