Bert - in order to use this plan, you have to buy both a SIM card and the bigtalk card you mentioned (it's a topup card for the pay as you go "big talk" plan) so you will be looking at more like 250 shekels.
You probably have to go to an orange store to get these things (usually random stores only sell monetary topups and I don't know if they will have an iphone sim). There are quite a number of them in Tel Aviv - including at the Dizengoff centre. If you can read Hebrew or get someone else to, the list of stores is here:
It may well be that specialist travel SIM companies have better deals than the Israeli providers, as the pay as you go Israeli deals available to non-citizens are often not a very good deal, especially if you have a short trip, as you have to factor in buying the SIM, and also actually finding the place to get set up.