Good intel, thank you!
I tend to use my merits for Converters for conversion roulette, Winter IOs, and Purple Recipes. Never thought purples would be so low, but to be fair I do check the purple price before using merits. If the price is over 20 million and I want the purple NAO I just use merits.
That being said, I look at it slightly different. Merits are free and I can earn 200 merits a day by doing a Hami raid and a TinPex, so I will typically run that content until I have all the purples I need for a character and then go back to normal marketing.