This is the exact question I asked when I got back into ice fishing.  It sure seems like a good amount of coin to plop down for that Marcum flasher only to see what depth of water I am fishing in.  But alas, there was my problem in thinking.  Seeing the depth of the water is an after thought compared to the true value of the flasher: seeing your bait on the screen along with the fish and how they react to your bait.

Yes, you can literally see your bait jig up and down with your hand on the screen.  Better yet, you can tell if any fish are around the hole you are fishing.  A popular method it to simply drop your Vexilar flasher down the hole and look for marks of fish on the screen.  If you don't find any, move to the next hole.  In other words, don't waste your time on a hole with no fish!

Sounds too good to be true, but I assure you it isn't.  I have followed the exact same pattern and fished more productively and have seen better catch rates because of it.  Plus you can watch the fish as they rise to take your bait and watch their reactions as you jig.  Perhaps they want a slower jig or a dead stick.  The flasher will tell you that instantaneously. 

A flasher really is a must to take advantage of the modern ice angler's way of life.  I guarantee it will put more fish on the ice for you. 

Do you have any stories to relate in regards to fishing with and without a flasher?