Opinions wanted

I am not sure you are understanding here. To PROPERLY prepare the top for vinyl, you will need to make it as perfect in prepping as if you were going to paint it. That's what the factory did not do, that's why they rusted.

So, in terms of cost, it will be almost the same as if you were painting the top. You should let the want for the vinyl top be your litmus test, not the cost, because the cost is virtually the same either way to prep it right.