I do calculate depending to see how much i'm getting for my points but sometimes it breaks down to if i want to spend the money or not. For example, no i may not redeem 20k points for a $100 room but maybe 10k? But like our future trip back to CA, we wanted to splurge on first class so where trying save and book hotel on points. So i look at the overall vacation and see where the better use of my points is if its "close" to the value that i have assigned my points lol
but yeah to be honest typically 100 or less i just pay cash because chances are i will find a much better rate for my points. I will say i also live in Miami and have florida as my backyard so there is no shortage of "expensive" hotels i can redeem last minute at without feeling bad about hoarding my free night or points.