Hi adeane,
That depends on the relative value of a local purchase compared to an online choice that uses similar materials and has a similar design.
The steps I recommend following with any mattress purchase are in post #1 here (and I would always start with local testing where possible so you can become familiar with different materials and designs).
Once you have narrowed down your final local choices then you can make more meaningful comparisons to similar online choices in “apples to apples” comparisons based on your own personal value equation.
I generally suggest that a “local premium” of about 20% or so would be roughly “equivalent value” to a similar online choice because of the lower risk of buying a local mattress that you can test first for PPP but the percentage that you may consider to be “equivalent” would depend on your own risk tolerance and your confidence that an online purchase would be suitable for you.
You can read more about the pros and cons of an online vs a local purchase in this thread.
Phoenix