It's not news that there is a charge for the toll road itself in addition to a per-day fee if you access such roads using a rental car. In fact, I think the rate charged has always been the highest "non-discounted" rate (plus any fees), so I'm not sure where you got the information that you received some sort of preferential pricing before. For example, when using the ETR outside of Toronto, the actual toll paid by tollpass users in rental vehicles is the same as those users with a personal transponder, however, because tollpass relies on the cameras to run the billing, renters pay the toll charge plus the "camera fee" (which varies depending on what part of the road you're using).

Keyword here is, of course, "optional" so renters are always free to opt out of Tollpass/sunpass/etc. at the counter or exit booth.

Frankly I don't find this practice any more objectionable than some states charging a higher rate to out of state transponder users (i.e., using a non-NY EZPass in a NY EZPass location).

The easy solutions here are to 1) opt out, 2) find another route, 3) use your own transponder/tag (if possible), or 4) accept the fact that some states have monetized infrastructure in this way and tourists like you and me are footing the bill. You can always vote with your wallet and skip the Florida vacation next time