75% reserve is an absurd ratio. If it's being held for more than a month, that's effectively an interest free loan to Etsy. No manufacturer of any size I know of would ever accept those terms without a contract that binds the supplier to purchase a set amount on a regular basis - you simply can't make money that way otherwise.
Regardless of the advantage of adding tracking to a package, the way Etsy is implementing their policy is clearly abusive to the sellers. 3% (like Amazon) would be reasonable. 75% is highway robbery.