I had been researching rates. I picked some dates that were basically weeknights (check in Sunday- Check out on Wednesday). I got a rate of $127 per night for the 3 nights. Now I research adding on the Saturday night at the start of the trip. I knew the Saturday would cost more but I was shocked to see that the rate for Saturday ($157) if booked now made every night that price of $157. So if someone is not paying attention instead of just paying one extra day at the $157, the hotel has now gotten an extra $30 from you for each of the next 3 nights.
In this case my dates changed and the I booked similar days of week for a different week and could not replicate this error, but the dates I originally checked are still coming up that way. If I was going to keep the dates listed, I would have booked the Saturday night on a separate reservation so it didn't trigger my entire trip. None the less, it's something to be on the look out for on any website.
I always research a ton, but happy I got this error so I could share!