Travel insurance for an adult in Europe is about £20-30. For a child it's less - about £15. For the USA (because medical care is more expensive) it can run up to £40. But the trick is to get an annual policy if you are planning to travel more than twice - around £50 - 70 per year.
We have ours through the bank, so it costs us nothing but is very good cover.
In terms of understanding policies, get hold of the policy and send an email to the insurance company saying 'I don't quite understand this, could you confirm I would be covered if: , etc. and keep their reply safe. Their staff will answer in more plain english than the underwriters.
In terms of percentage costs of your holiday it's probably less than buying breakfast for your family at the airport
. And yes you can rely on emergency care on an E111 but rehabilitation is not always covered and repatriation will never be covered. As Elenio has pointed out, sometimes not even nursing/bedding is covered beyond the basics.
Nor will repatriation of the body. We've just been through this because MiL is in Australia and she's very old. We spoke to the insurance company and they told us that in the event of her death they would give us the choice to have a funeral over there and fly a couple of us out or repatriate her body (it's actually cheaper for them to fly two of us out business class than fly her body back). (She's not dead btw, she just wanted to know so I phoned them).
However it's worth saying that you need all members of the party to be covered. If your spouse breaks his leg and needs to be hospitalised and you miss your flight, it's your insurance that generally covers this. So it's worth asking about a 'family' policy or a 'group' policy so administratively it's more simple to organise.