My problem with abstract estimates are as a product manager my dev team cannot seem to provide me a time measurement that will allow me to accurately bill my cu

My problem with abstract estimates are as a product manager my dev team cannot seem to provide me a time measurement that will allow me to accurately bill my customers for custom feature requests to recoup development costs and hopefully make a little extra. So abstract estimates might be good for determine sprint velocities…and may be great for carving up releases, but they suck when you are doing custom modifications you need to accurately quote before the work begins. Because I also have a development background too, I just tend to look at custom features through through the lens of “how much time this feature would take me”, then add a few multipliers and cross my fingers that the faster and better devs pickup those stories so we don’t lose money.