I paid $2100+tax for my turquoise egg with the thin chain that I plan to replace. I believe the chain is $300. This makes the current price of the turquoise egg ($2100-$300=$1800).
I believe the Lapis egg price is slightly lower that the turquoise according to @meesmom at the time she was buying hers several years ago.
I would not pay more than $1500 for the estate lapis egg if it is the small size. However, this is just my personal opinion and how I feel about it.
I would pay up to $2000 if I was getting it from the store.
Good luck with your purchase and remember that you can always negotiate the price with the seller.