I just look at current in-stock retail prices online and base the trade ratio on those prices.I do not think that there is a constant ratio for prices for different items.
small pistol primer prices are up as much as 8 to 1. 9 mm prices generally are up about 3 to 1. That may go higher. If factory 9 FMJ is selling at 1$ a round I do not think that there will be a shortage at that price.
I will have a lot of it to sell.