Need Help To Value Irish Stamp

I just won a couple of album pages of older Irish stamps on one of the sheets there are 2 seahorse overprints 2/6 . There are a few different types of this overprint, when Ireland won its independence from Britain they used overprints for quite a few years. I know the lowest value of this stamp is the Scott 77 and wonder if anyone has a current catalogue and would be kind to tell me what the CV is for this Scott Ireland 77.
There seems to be a lot of high value Irish stamps being sold at the moment manly from the states. Is this a sign of people selling off there collections ?. I know there are over 40 million Irish descent in the USA and people quite often collect stamps from there families country of origin.
What I am seeing is lots with a CV of $1000 or more being listed with out a reserve price and being sold for 20- 40 dollars.

The stamps in question ar the bottom right and bottom left

irishjack (love the name )

There are a number of overprint varieties of these stamps from years 1925, 1927, 1927-28, & 1935. Could you individually scan the two stamps in question?