I also stayed at the Marriott Moscow Grand Hotel and interestingly had wondered about breakfast in the lounge as well (though I knew it was served, just not what exactly was served) and got the answer about coffee/bread/butter/jam and then had my friend a Russian call and speak to them in Russian and the person on the phone elaborated more than just coffee/bread/butter/jam and gave a better description (exactly what at this point I cannot remember).

Regardless, my Wife, buddy and I chucked it up to the hotel employees being more comfortable in their native tongue and thus were able to elaborate more on the offerings than when I queried them in English.

I never thought scam (maybe I am naive, entirely possible), just more of a language barrier issue.

BTW the breakfast in the restaurant was materially better than the offerings in the lounge and while were were not offered a set price (like the original author here), we felt it was basically worth the money and for $25 it would be IMHO worth the money.