Hi Petex,
I’m not so sure that either Ikea or Sleep Innovations would be a great choice for a memory foam mattress but as you mentioned Novosbed is included in the list of some of the better memory foam options I’m aware of in post #12 here and the Canada list as well. It will also depend on the specifics of the mattresses you are considering and which one would be a better match for you in terms of PPP.
There is more about the factors that can affect durability and the useful life of a mattress relative to each person in post #4 here. A mattress that doesn’t have an obvious weak link in terms of durability would definitely be “worth it” to me.
No matter what the cost of a mattress … there would be little “value” in a mattress that only had a comfort life of a few months or a year or two before it needed to be replaced.
The better options or possibilities I’m aware of in the Vancouver area are listed in post #2 here.
Phoenix