We are going to start a Plinko Poker Promotion at my local card room and the board is set up as follows:

9 spots at the bottom, 1 ace, 2 kings, 2 queens, 2 jacks, 2 tens.

A player earns a plinko drop through a number of different ways that are irrelevant to this post. When a player earns a plinko drop, the player draws a plinko disc out of a bag. There are 4 discs in the bag each of which has a spade, heart, diamond, or club on them. This represents the suit of the card that your disc lands on. You then drop your disc on the board and you earn a playing card.

We are giving away 3 progressive prizes:
Quads (kings through tens)
Royal Flush
Quad Aces

I've had some conversations with a few people and there is a mixed opinion as to whether or not a Royal is harder to make than Quad Aces. My calculations are below, and I'm just asking for confirmation or feedback as to which is more difficult. I show 4 aces to be roughly 5 times harder than a royal. You must have a 5 card hand to qualify for a prize. Also, if you earn a duplicate card then that is equal to a ZERO (so you can't have 2 ace of spades or 2 queen of diamonds etc). However, different players can have the same cards.

4 aces: (1/9) (3/4 *1/9) (2/4*1/9) (1/4*1/9) (8/9)=12.7 out of 1 million

Royal: (1/1) (1/4*7/9) (1/4*5/9) (1/4*3/9) (1/4*1/9)=62.5 out of 1 million

We are also toying with the idea of making the prizes Quads, Royal, 5 aces (4 of different suits). I came up with 5 aces being made 1.6 out of 1 million times on the first 5 cards.

So, in conclusion I have the hands ranked from easiest to hardest as follows:

Quads, Royal, 4 aces, 5 aces.

Are my calculations correct?

Also, players keep their cards over time; so a player will eventually win whether it takes 5 cards or 25 cards.

Thanks.