While a mining profitability calculator would be nice, I see very little value in having a calculator go from RAC --> GRC/day. The difficulty is reaching a good estimate for RAC in the first place.

I think you're just too smart a guy to understand how helpful that would actually be. The average Gridcoin miner is not actually intimately familiar with the reward calculation. That's why these calculators have existed in the past and why we get people coming into the Subreddit on a weekly basis pointing out the fact that Katieee's calculator doesn't work and suggesting that we should set up a functioning calculator.

Some people do hide their machines, but if you use the "top computers" list, you can see all the machines (it just attributes hidden machines to an anonymous owner) and very easily gauge RAC potential for your hardware.

Once you have that, you and I could just grab our calculators and do the rest of the math ourselves, but most people can't do that.