How many extra moves can 10 gold bars get?
My own experience in using gold bars to get extra moves has been:
10 gold bars for 1st 5 extra moves
+16 gold bars for the next 5 extra moves
+39 gold bars for the 3rd installment of 5 extra moves
+39 gold bars for the 4th 5 extra moves.
That's as far as I've gone for my ow account (currently at level 14661)
So it cost me 104 gold bars for 20 extra moves.
But I've read from other players in this forum mention that by failing the same level repeatedly until you get the offer for an extra 125 moves.
Since there's not much happening in the game, for me anyway, no Road Trip Collection, nor Beach Quests, I have decided to check using one of our family's inactive account (got stuck at level 14239, with 1 gold bar and very few boosters left).
After 1 failed attempt, I got an offer of 10 gold bars for 20 extra moves.
Better offers followed every new failed attempt : +5 extra moves on top of the previous offer. I'm taking a break at the offer of 10 gold bars for 135 extra moves, after altogether 23 repeated failed attempts
See, King does want us to pass levels, even those legendary levels, offering 135 extra moves for as little as 10 gold bars!!. Additional offer is given too for a "irresistible" Tasty Testers bundle:
Thanks, but no thanks, I'm not spending money, definitely not on this account. It started off building healthy stock of boosters and gold bars (still having 5000+ @ 3 months ago). Overuse of powerful boosters, UFOs and Party Poppers (purchased using gold bars), bankrupted the account. It's poor management of resources, but my guess is that he wanted to quit the family game.
For him, it's time to say good-bye, with some fond memories, I hope.