Really depends on how hard it is to get because if you can get 100 gold just by playing for a couple seconds why waste it however if it takes like an hour to get 500 robux then it makes sense and more people will probably buy it
The 100 gold and 10,000 gold devproducts exist strategically to intervene at points of crisis. There are two major grinds in the tycoon, one is at the very beginning, where you have to click a lot to get a decent amount of gold, and the 100 puts you at a good place, while the 10,000, apart from being almost an absurd amount of cash, allows you to get “over the hump” of buying some extraordinarily expensive items.
It depends on what you can buy with gold in game. In terms of marketing, the strategy of making it a better deal to buy more is a good idea, but your baseline (smallest purchase) should be based around what gold can get you in game, so the rest of them are realistic/reasonable purchases for your players.