The ships are to be fitted with Russian sensors, C4I, and weapon systems after delivery. What the Russians are paying for basically is a modern hull and propulsion system built to 21st century commercial standards. Being build to commercial standards means the structure of the vessel is not as heavily reinforced as a warship. Think employment in humanitarian assistance/counterinsurgency/low intensity conflict scenarios. Perfect platform for intimidating your weaker neighbors.
Yes, they could develop this platform themselves but then there would be all that duplicated effort in engineering and development. Not to mention the time it would take to accomplish this.
I am probably wrong, but I seem to recall the original deal was for two French-built ships with options to build more in Russian yards. If the French limit them to one, the Russians will reverse engineer the single ship they are going to receive and build the numbers they need.
However, nothing they acquire or build can cure the strategic problems for the four Russian fleets created by the lack of direct access to the open sea. Each is constrained either by multiple, uncontrolled straits they must pass through (Baltic and Black Sea fleets) or by being ice bound for part of the year (Northern and Pacific fleets).