There's no way to get ice besides the Empire Shop, so it's unlikely you'll find anyone selling it for less unless it's a loss leader, and with teleporting there isn't much point in loss leaders. [Edit]In Economics 101 terms, the Empire holds a natural monopoly on ice because the barrier to entry is insurmountable due to the Empire's total control of the resource. Because of this, our Benevolent Leader can charge whatever he wants.
You can't get ice on EMC any other way i believe, I haven't used silk touch yet but i'm 100% sure it doesn't collect ice. If you want ice you will have to buy from the empire shop unless some generous player buys for 50r from the empire shop and then sell's it for a lower price but i don't see that happening. If you want to use ice to build i think you can buy one block and if you put water next to it the water will freeze, i have done this but only in a snow biome so i'm unsure wether it will work on your residence.
It doesnt work in town, I have ice blocks in my little pond and it does not freeze the water around it. And jeah thats right you have to buy it in the shop it is not obtainable through any other mean.
You used to be able to get ice with silk touch but it was removed in 1.0. So someone could have a load of ice blocks they gathered earlier and now want to make some quick rupees.
Silk touch for ice only worked in the prerelease which the server didnt ever run.(I think I wasnt there at the time.)
@jackomighty I'll buy 20 (= 900 r) @FooHundred Thanks, I was thinking that somebody could get some with silk touch, now I know better :S
water can freeze in town in some residence that is in cold biome I saw EEJester did it once. 58x58 ice floor but later on he broke it and build something else on top of his res.