This is the 1.87% service I used:

https://www.pay1040.com/

It was the lowest-priced of 3 I got after using Express1040.com to file my taxes. Two of them were under 2%, the third was somewhat above it.

I used my Amex Premier Rewards Gold where I'm working on $1000 spend to get 50000 MR points. My $200ish in federal taxes (I'm getting more than that as a state refund) thus earned me about 10000 MR points, while costing under $4 in fees. I don't consider paying $4ish for 10000 miles to be such a bad value. Extrapolate: That's $10ish for 25000 miles (a domestic saver round trip), or $40ish for 100000 miles (a business class saver round trip to Europe or Japan on some airlines still). How can $40ish not be a good value for 100000 miles?

I only have to pay taxes after filing every other year or so on average (the other years I get refunds on both federal and state), but I can't remember the last time I didn't have a signup bonus going when I did have to pay.

As to value of miles in cents, it depends on what you redeem for. The value tends to be lower on domestic coach flights, but those I pay for in cash most of the time. The value tends to be much higher for longhaul international.