That's some very clear coverage, FoxRun.
What those of us who have also purchased PDE5-inhibitors in the past via prescription, dispensed by corner pharmacy (Walgreens, CVS, etc) have learned is that the $500 annual limit will pay for about 3 months worth.
This is, of course, why so many men who frequent these pages also use offshore mail-order pharmacies...and most use one in particular.
Here's what I did. (This is not necessarily a recommendation for what you should do, but simply what I did and what I have read here that lots of other men have done, similarly.)
First step is to find out which pill works best for you, or works at all for you. Your question of price comparison vs. effectiveness is, to an experienced PC/ED person, sorta off-base. In the bigger picture it's the wrong question to ask, but at your early stage in this learning cycle it is a cute questions to ask. Ask your doctor for free samples of each of the pills (he/she may only give them to you one at a time and say, "try this one first"). Not all the pills work for everyone, and some don't work at all for some few numbers of guys. This may take a while, but find the one that works for you. If you can use free samples at this very, very early stage, good for you, if not, burn some of your coverage.
Second, after you find something that works, go ahead and burn up the rest of your prescription coverage. You'll be surprised how much your own 20% contribution adds up to be. Depending on how active you want to be, your limit will be consumed well before the year is up...well before. Again, I'm really just describing my own experiences here, so substitute "you" with "me," or the proper form of the first person.
Third, the first online purchase of that very same pill might want to be a small order. I believe I placed two relatively small orders so I wouldn't be out more that about $50 if the place wasn't legit. Not a big deal. Once confidence was gained, I placed larger orders. I don't remember exactly, but I think about a year's supply is in the range of $125, or something like that. I've got probably a year plus supply in my drawer now.
Effectiveness versus cost comparison....that's cute!