[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"]
Starting a game with a total of 78 point-value, how many legal moves are required to produce the maximum total point-value on a chessboard?
Of course, promoting all the pawns to queens must be done. Creating sixteen passed pawns requires sacking eight pieces, four per side. The sacked pieces should be the knights and bishops to preserve the higher value pieces. From there, it's merely an "Onward, ho!" to a total point value of 182, which comes from the nines queens and two rooks on each side.
Here is one example game in 51 moves, or 102 plies. Since getting 18 queens alone takes 48 moves, or 96 plies, this is almost optimal, I feel.
[FEN ""]
[startply "102"]
1. c4 f5 2. c5 f4 3. c6 f3 4. b4 g5 5. b5 g4 6. h4 a5 7. Nh3 Na6 8. bxa6 gxh3 9. g4 b5 10. Bg2 Bb7 11. cxb7 fxg2 12. h5 a4 13. h6 a3 14. Bb2 Bg7 15. hxg7 axb2 16. a4 h5 17. a5 h4 18. e4 d5 19. e5 d4 20. Nc3 Nf6 21. exf6 dxc3 22. d4 e5 23. d5 e4 24. f4 c2 25. f5 e3 26. f7+ Kd7 27. f6 e2 28. d6 c5 29. Kd2 c4 30. f8=Q c3+ 31. Kd3 e1=Q 32. g8=Q b1=Q 33. a7 Rc8 34. Rf1 Qde7 35. f7 g1=Q 36. Qh7 Ke6 37. d7 b4 38. a6 b3 39. a8=Q h2 40. a7 Qa2 41. b8=Q b2 42. Qab7 c1=Q 43. a8=Q Qf4 44. g5 c2 45. g6 b1=Q 46. g7 h1=Q 47. d8=Q Qhg2 48. g8=Q h3 49. Qfg7 h2 50. Qge8 h1=Q 51. f8=Q c1=Q+