You will get clobbered if you attempt to do this on slots, which have a high casino hold.
I believe the good machines at Cromwell are $50 per tier credit, rather than $10 per tier as they normally are for video poker.
Unfortunately, to my knowledge, there are no good video poker machines in Vegas giving 1 tier per $10, except at really high limits ($25/credit).
The only 99%+ machine is the Double Bonus Poker at Rio (see page 1 of this thread). But that's a single play dollar machine, and will take forever to earn tiers (basically one tier every 2 hands).
Perhaps take a little trip to Tahoe to play the better machines there?