If I recall, I paid about $300 for a r/t between TLV and CAI on El Al. This was a discounted economy ticket I bought a few days before departure while in Jerusalem. The flight on El Al was short and pleasant enough.

If you have never been to Jerusalem, I highly recommend it (although I would also keep track of the latest developments in the region). Cairo is equally, if not more, fascinating, although you may want to check when Ramadan is (my two New Years trips to the Middle East have both coincided with Ramadam). Traveling during Ramadan is not ideal, but it is definitely do-able.

Although I recommend visiting Jerusalem, here are two downsides to visiting Israel before going to Egypt.

1) You will likely forget to ask that your passport NOT be stamped by Israeli immigration. If you want to travel to most other countries in the Middle East, you will need a new passport without that Israeli stamp.

2) If you are traveling by yourself and fit the "profile", you will most likely spend an hour or more each time you are in TLV or CAI answering security questions and having your bags physically searched.