Blackstone charges $32.50 for a UOA, including TBN; $22.50 without TBN. Being a bit of an oil nut, I always ask for a TBN.
Their sample kits are free, and they'll send your results in an e-mail if you want.
Personally, I think it's worth it to have a UOA done each, or every other, oil change, just to keep tabs on what's happening in there. The last one they did for me on the X595, there was a high silicon (dust) reading - I'd changed the air filters, and one of them wasn't seated properly. That $32.50 probably saved a bunch of $$.