Fairly rare - that's an understatement.

So hard to find these at reasonable prices.
Appreciate all the replies. Is there a source for Greysheet pricing online? Don't have access to these; thanks GR for posting. I guess maybe I need to spend the money and buy something like a
RedBook.
Here are my prices based on a combination of Heritage,
ebay completed auctions, Numismedia, PCGS and a decent Lincoln site I have used in the past. First price is what I would like to pay; second price is probably upper end for a really nice example:
1909-S $300-500
1913-S $265-425
1915-S $280-450 (I seem to be low here)
1918-D $150-200
1918-S $180-240
1924-D $360-570
1926-S $570-1170 (looking below, I may be high here)
I was happy that I was able to snag a nice 17-S ANACS 63-RB for $245 recently. My range on that was $150-330.
Here's some items I am tracking on Heritage that just ended:
7249 Lincoln Cents:
1915-S 1C MS63 Red and Brown PCGS. Sold for $900
($1,057.50 w/BP)
7261 Lincoln Cents:
1917-S 1C MS63 Red PCGS. CAC.
Sold for $320
($376.00 w/BP)
7285 Lincoln Cents:
1926-S 1C MS62 Red and Brown NGC.
Sold for $600
($705.00 w/BP)
7286 Lincoln Cents:
1926-S 1C MS63 Red and Brown PCGS.
Sold for $600
($705.00 w/BP)
7287 Lincoln Cents:
1926-S 1C MS63 Red and Brown PCGS.
Sold for $575
($675.62 w/BP)
25497 Lincoln Cents:
1913-S 1C MS62 Red PCGS. (this one looked like it had turned brown in the holder)
Sold for $220
($258.50 w/BP)
Looking at
ebay at the moment, I see (these may be overpriced in some cases - I should look at completed auctions):
09-S A really nice PCGS MS64RB for $530 (need to save some money up)
13-S No 63's; there's a beautiful 64 for $699
15-S Nothing decent, even the 63BN's are asking $500+
18-S Couple of nice 63's in the $275 range
24-D Slim pickins
26-S There's a decent 63 for $939
Gonna post all this so I can go back and look at everyone's responses and maybe make some adjustments in my targets.
This has been pretty helpful for me actually, thanks!