Exactly when you run together, your VSP cost or your dental plan cost and compare it to the uninsured cost, it often is the same number. What it does do is get you out of the BS grossed up number for the work and get you down to the actual number that the practice needs to make a profit. That can be useful if you're going to have ongoing costs during the year.
For what it's worth, don't assume that you're actually getting the correct discounted rate. I had a dental plan and the provider paid lipservice to giving the correct negotiated rates but then would bill at a higher rate. I would come back and show the schedule cost that they agreed to with the insurer and require them to honor it. The insurer wasn't particularly helpful. Other than to say "we will call them and remind them of their obligations under the agreement."
For what it's worth, my wife had some dental work done and reflexively paid the amount she was told was due by the provider. I am still working with them to get back the overpayment. I'll get it eventually, but the song and dance is annoying.