What To Do? I Can't Afford The Final Coin In My Set...

That is really cool! If only I had the time, equipment and skill.

I'm sure this has been said ... and with all due respect ... why is this an issue for the OP?

I assume nfine completed the research needed to know and understand the coins and costs involved in this endeavor ... sooooo ... why choose a set that you know will disappoint you somehow at the end?

Makes no sense to me ...

Education is the key ... and that is the purpose of the CCF.

nfine, I'd recommend putting the Sacagawea dollar set on hold and letting the Cheerios dollar come to you in time if possible. The Cheerios dollars have been trending down over time, though I think that they're probably near a bottom. I was able to get mine in NGC NS-68 for $5,405 from a Heritage auction. You never know what will happen at an auction. The opportunity for a MS-65 might come to you for half that.

Do get the Goodacre Presentation Sacagawea dollar if you don't already have it. The mintage is similar to the Cheerios dollar, but there are many more actually available.

I personally do consider both the Cheerios and Goodacre Presentation dollars to be die varieties. I do include them in the set because the mint intentionally made them. Another example of a coin that I'd consider to be a die variety would be the 2008-W Silver Eagle with the 2007 reverse. Again, it was intentionally made by the mint. I don't consider errors like the 1922 plain Lincoln Cent to be part of a set. Others here have said that they don't consider these die varieties part of the Sacagawea series. In the end, it just comes down to what you want and can afford. If you save over time, you can get there if you want to.

When I started 2 cent pieces they were affordable for me, even the 1872. When I started the nickel 3 cent pieces they were affordable for me, even the 84, 85 and 87. When I got to the 1872 2 cent it was salty and a stretch but I got it. When I got to the last two nickel Three Cents they out of my reach. That was back in the early 90's I make more money now and I've managed to get one of the last two but the last one may still be out of reach. You can do the research and start with a reasonable goal, but sometimes the goalposts move on you.

Start another set that would be impossible to complete.
That is how I started into ancient coins.
That was nearly 40 years ago.

Yeah the Wounded Eagle is a lovely variety and check your change and all. You never know what you might find. I was looking at an auction site and went to view the coins and I saw a Wounded Eagle Dollar coin in the mix of dollar coins and bought it (it was in a roll) for $35.
Research and keep looking

I've pretty much just accepted the fact that there are certain holes in my Danscos that will never be filled. If I get feeling bad looking at them, I just pull out one of my filled albums and go through those until I feel better. I think I am slowly changing my enthusiasm towards type-set collecting as opposed to complete sets, but that's just me.

Join the crowd nfine. I'm in the same boat, don't feel bad. Whatever you have your heart set on to collect and complete, stick with it. With that said, I have tried to stay away from series/sets that I know will get me in trouble (difficult to complete/most are) towards the end.

Right now I'm just trying to stay focused on completing a Washington quarter Dansco set. I only need two more. I drove down to the Whitman show in Baltimore on Thursday just to see what's out there, available and prices. I'm not ready to pull the trigger. Between you and me, I should have just saved the gas, toll and parking money and put it towards those last two coins!