We got for this summer tickets AMS-ORD at a cost of 195€ in taxes + 52500 miles, in Y. Compared to the tickets costing 980€ (without luggage, so more like 1030€). I consider this as an ok deal
Depending on what status you have with FB, to get 52,500 miles you have spent between 6,500 and >13,000 EUR to get those miles. Optimal case, 6,500 EUR spend on previous tickets + taxes of 195 EUR for a ticket that would have cost 1,030 all in, that is a discount of 8.5% on your ticket price.
Entirely up to you if for you that is a good deal or not.
(For comparison, I snatched a Premiere award CDG-LAX for 200,000 miles plus EUR 305 in taxes. Paid fare would have been EUR 12,846. To gain those 200,000 miles I had to spend EUR 25,000, so all in all I paid EUR 25,305 to get a ticket that if bought would have cost EUR 12,846. Very sweet deal. But I realise that this is an extreme example: I really only needed a one-way, so the EUR equivalent was relatively expensive, On a return basis the CDG-LAX priced out at EUR 8,028. And I think if dynamic pricing had worked correctly it would have been 350,000 miles like on most other flights that only sell the top fares.)