Hi rdubb21,
As you know your budget is very low so there aren’t a lot of options available in your budget range that use good quality and durable materials.
There may be some local options available to you (including some of the better quality Ikea mattresses) and if you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of in your area.
Post #4 here includes some of the better online options I’m aware of that are in lower budget ranges.
There is more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) in post #2 here that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for once you actually sleep on your mattress.
There is also more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses in terms of suitability, durability, and “value”.
I would always keep in mind that a mattress that has a good price and uses good quality and durable materials but isn’t a good match for you in terms of “comfort” and PPP (which is all about how well you will sleep) or that is a good match for you in terms of PPP but doesn’t use durable materials that will maintain their comfort and support for “long enough” (which is all about how long you will sleep well) would both have little “value”.
There are also no “standard” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions about the firmness of a mattress or how two mattresses compare in terms of firmness as well and some people may rate one mattress as being firmer than another and someone else may rate them the other way around. This is all relative and very subjective and is as much an art as a science.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart who can help “talk you through” the specifics of their mattresses and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked that they are familiar with, any special considerations you may have, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs or firmness options to different body types, sleeping positions, and preferences or even to other mattresses that they are familiar with than anyone else.
Phoenix