Years of experience - how to count PhD and postdoc years
Ok, let's see: First of all, Data Science is a relatively new field, Data Scientists are in high demand in many places, so estimations on salary are difficult to make, statistics found online are mostly not representative as there is not yet enough data.
Next, the fact that you have a PhD should count stronger than the mere years you spend on obtaining it.
And as a third point, the work experience always depends on what you did and what you plan on doing. Imagine you worked five years as a baker. While this is job experience, it might not be very relevant for a job (and salary) as a Data Scientist.
If you think that your years should count as experience, then make that clear, argue your case, show that you actually have experience. Salaries in the industry are usually not computed by a fixed formula taking your degree and years of experience as input but are up to negotiation (inside certain bounds), so if you can convince your future employer that what you did counts as experience towards the job you are applying for you can of course ask for a higher salary; if you yourself are not convinced then maybe you can't; but then again, having a PhD and the basic requirements to become a Data Scientist already means a rather high salary in many countries and areas.