Hi navigates,
Sales that claim to be 50% off are a major warning sign because the 50% is based on a price that nobody ever pays. You can read more about “fake sales” in the industry (where prices are marked up only to be able to mark them down again to make the sales look real) in post #5 here. You are not getting any kind of a “deal”.
While only you can decide which mattress is the best match for you in terms of PPP (which is why it’s so important to know how to test a mattress) … all of the choices you are considering would be a very risky and would use lower quality less durable materials compared to many others that would be available to you made by other manufacturers in the same or better budget range.
Phoenix