This will probably be off a couple cents because of the Roblox teams' lack of consistency. (For example, 80 robux can be bought through mobile devices for 0.99$ Yet if you buy it through Rixten it is 1$, This causes me to have to round the difference between robux and dollars to multiply the robux by that to get the amount of money it is worth.
I just noticed DanTDM used this, and I would like to thank you guys for your support. A lot of you have been talking about how this is slightly inaccurate and I would like to let you know that this uses the average of the Roblox prices as Roblox does not make it consistent. This does not use dev ex rates, this is just to see much real money you need to spend to buy an item.