Some places make them for yachts any size etc out of memory foam. However, I don't know if you can call the price efficient. A mattress designed for a house would be cheaper, but can you get it in there.
Actually the prices among custom mattress manufacturers vary a lot as does the quality. If you find a local custom mattress manufacturer it may be no more expensive than mattresses at retail because they sell direct and no added costs from the channels of distribution. The other part of the custom market is the luxury part where it will be expensive but still no more so than equivalent retail mattresses and often better quality. We thought custom mattresses only made sense for odd shapes and sizes until we purchased our first one and loved how it slept. Now all our mattresses come from the same manufacturer.
Just buy a memory foam mattress from costco or amazon and cut it yourself. Or most upholstery guys have the blades to cut foam as well. From the "Boating mattresses" that i have seen they are way over priced
There are different types of mattresses available for boats. The problems start and the prices go up, if you need custom sizes and shapes. It starts with simple 4 inch of foam, covered with some fabric and made at home. You will hate that mattress after you first night. The most expensive but by far the best type of mattress is the pocket spring mattress. Custom made in odd shapes and sizes and 5 star hotel quality, they get quite expensive, when bought from manufacturers specialising in the yachting industry. Almost as good are the memory foam type matresses, if it is high quality foam. Memory foam has the tendency to get warm and needs top layers of latex foam for ventilation plus a ferfect made and fastened fabric cover. Buying plain sheets of memory foam and latex foam and cut into needed size and shape at home, needs some sewing skills, knowhow and time. You may end up, using your "first trail and error" later only for your dog (or mother in law) . Price-conscious boaters in Europe go to shops, which produce custom made matresses for campers and motorized mobile homes. They are much cheeper than the used to luxury (prices) yachting industry. Just my 2 (Euro) cents
There is no better sleep than on a good foam (NO spring) mattress on a boat that is on anchor. My choice would be Tempur-pedic, after you have one, there is no turning back! http://www.talkofthedock.com/gear-reviews/cabin-a-galley/339-tempur-pedic-mattresses-for-boats/
PacBlue, I agree, that is the best stuff one can buy for his boat. But I had the feeling, the OP wanted with an "efficient way to replace" exactly avoiding this price level.
Following HTM and Blue, we place an extremely high importance on the right mattresses. A comfortable, make that extremely comfortable, is a luxury we find worth having. Now what that is varies among people. For PacBlue it's Tempur-pedic. For HTM, it's pocket springs. Three years ago we purchased our first custom mattress and the only reason we bought custom was the size. 10' x 12' isn't a mattress size normally carried in stores. It arrived, we slept on it. We bought every boat mattress from the same people and then all our other mattresses at home. You spend nearly 1/3 of your life on your mattress, and how you sleep on it has a great deal of impact on the other 2/3. Quality mattresses are available at a reasonable price, although not a cheap price. The standard mattresses most often seen on boats are both overpriced and lacking in comfort. I measure by wanting at least the same comfort as home.
While we don't buy our mattresses locally, I will say you'd be shocked how many local mattress manufacturers there are in most areas who will custom build anything you want and are not expensive. Typically they're manufacturing a small number of mattresses for the independent mattress shops or selling in their own store front.
I was taking efficiency to mean less about price point, but maybe something quick and easy. Since the OP has stated he was going to live aboard (from previous posts) I would think this would still fall in his price range. And if you are living aboard, I certainly would take Olderboater's approach and make sure that it is really comfortable. I think spring mattresses are better suited to the land side and do not prefer them in a structure that moves (with the ocean) in a dynamic environment. There are also some new designs/technology that is being taken from the medical field where they treat burn victims, to create a weightless (without pressure points) design. But price is all relative, and when it comes to really expensive mattresses, Tempur-pedic doesn't even register. I see custom manufacturers who are targeting the top 1%, and then you start talking $50K+ for a mattress! Complete with "hand teased horse hair" and the like - Something like this: http://www.hastens.com/en-us/vividus On a 130' MY, we made sure to build a seamless and removable "hatch" over the Master Stateroom, that would be just big enough to replace the owners King sized mattress. Comes in handy when it is time to replace the soft goods.
Capt Bill11, that is a nice link. It explains the different types of mattresses quite good. Choosing the the perfect type of mattress for your purpose and your personal requirements is not only a matter of budget, it is also a matter how you sleep at home and what level of comfort do you expect on your boat. And it is partially ideology. I agree with PacBlue, the old fashion spring mattress with the metal skeleton and springs, covered with a layer of horse hairs and a thin layer of whool is dead. Modern highly comfortable and high quality mattresses are a perfect ergonomical combination of different foams, latex foams, sometimes pocket springs and other materials. Prices go from less than 100 $ up to the costs of a good sized car. But as important as the mattress itself, is the supporting well ventilated structure under the mattress. The memory foam, invented for the conformal astronaut seats / beds is a fantastic material and if constructed correctly, the best available material for long term patients in hospitals and elderly homes. I personally could not stand long range flights of more than 4 hours anymore without my memory foam cockpit seat. And my collection of fighting spareparts (the helicopter) would have ruined my "Spondylitis ankylosans" meanwhile completely without the vibration absorbing memory foam in the cockpit seat. Will say, the type of mattress one buys is dependend on personal prereferences, personal needs, tastes and buget. But I will definately never sleep in a hammock again .
I bought on eBay a 10"memory foam mattress (look for the one with zipper cover), shaped it with a Stanley knife (easy job) and found someone with a professional sewing machine to correct the cover. All and all an easy job, saves you a lot of money and we really enjoy the mattress! Link: Ebay mattress
If you want to cut shape foam, get out the old electric meat knife. Works like a charm. Many shops use them.