You have paid for MOST of your food with your ticket. If you do not dine in Pinnacle but have all of your dinners in the Dining Room and/or Lido, you will incur no extra charges.
The $20 pp charge in Pinnacle is for the very high end, excellent quality menu selections that are not available in the Dining Room. The steaks in Pinnacle are on a par with the likes of the very best steakhouses and the fish/seafood is the best of the best. No cruiseship dining room can feed 1,200 to 1,800 plus pax that quality at the prices we are paying for most cabins on most HAL cruises.
A comparable dinner in a shoreside restaurant costs DH and me in the vicinity of $200-$225 if we share a bottle of wine similar to what we order in Pinnacle.
Tips are not figured in the per person extra charge.
It is totally voluntary to go to Pinnacle. If one does not wish to pay extra for dinner or pay extra for tips, there is absolutely no need to. Dinner in HAL's dining rooms is Excellent IMO but could never be at the extra high level of Pinnacle unless we paid a whole lot more to cruise.