For clarity I will name your cats to cat 1 and cat 2.
Cat 1 = Previously Blocked // Cat 2 = Healthy
For cat 1 keep him on the prescription wet food diet until your vet says otherwise, I would be afraid to switch him so soon and he re-blocks - they call it a prescription diet because it should be treated like a medication. You can price check from different veterinary hospitals as food prices will vary, the hospital I work at has much cheaper prices than other clinics around (10% difference).
If cat 1 picks at cat 2's food I would recommend that you feed Cat 2 more wet food - he may not have blocked yet but risks are much higher on dry food. Buy what's in your budget but keep in mind that with higher quality foods you won't need to feed as much (this varies from food to food) for your cats to obtain their daily nutritional needs. For example let's say a 0.50$ can of low grade food you'd need to feed 3 cans vs a 1.00$ high quality food where you only need to feed 1 can a day - you will also see increase in stool production on low grade foods.
Another thing you can try is called Surefeed this can be programmed to only open when a certain pet is near, it helps prevent unwanted food theft.
Water intake is very important to prevent cats from blocking: add a water fountain (cats prefer running cold water vs still), increase wet food, or add water to dry food. This allows them to pee more thus flushing out all the garbage. A cat that doesn't pee frequently (you will see 1 large pee in the box vs many small/medium pees) holds in all the junk that the kidneys filter out from their system and then you start seeing crystal/stone formations.
