Brian, I strongly suspect any solution similar to those in the photos you have supplied will be extremely expensive. As you have mentioned, you have already had one company provide a price which was at a price you envisaged. Unfortunately, a designer solution such as this is rarely scalable in terms of size, the fact that you are mobilising a designer, fitter etc. will carry a substantial price from the outset. The previous suggestions offered by professionals on this site suggested by B&Q and Ikea are clearly at a different price point, but nonetheless a solution to the dilemma you presented.

Due to the size / layout of one of our bedrooms we did not want a freestanding wardrobe and improvised very successfully with two of these mounted on the wall side-by-side: http://www.ikea.com/gb/en/products/small-storage-organisers/racks-stands/hemnes-hat-rack-black-brown-art-10245870/ Dust is the only issue on items that don't get worn. But that's also a good motivation to take stuff down the charity shop.

I personally see it different and don't mind how it looks. It will limit the sound coming from the bathroom and offers privacy. You will need to make it look more at home though.. maybe add a few hooks on the side for coats or dressing gowns, bags etc. This also massively depends on how the back looks as this sometimes doesn't look great. You can add a sheet of on the back and paint it and then add a picture or mirror to create a more interesting back area. By placing wall lights and art above/to the sides of the bed you will also zone the bed area a little better and make this whole area feel much more homely. I hope it helps. Don't be discouraged you'll get there :)

A well-designed sofa bed will not compromise on comfort. I would definitely check the height if you do go for one just to ensure it is okay for your parents. Alot of companies will also let them test it out for comfort before you purchase. We specify ligne roset sofa beds quite regularly for clients who want multiple uses out of their spare rooms. In your case it really depends how often the room is used. If your parents are sleeping there daily (or even weekly) a double bed would be preferable. And as Carolina has mentioned the opened dims of the sofa bed would take up as much floorspace as a double, but I'm sure you are aware of that, as that is the point in them :) But by using one the room could have more than one purpose. It could be used as a reading nook for example, but multiple other uses throughout the day (even ballet...).