I went to Yi's upholstery in Rockville with the same issue. It was going to cost at least $500 to do just the back cushions on a relatively small sectional (90x105.) Priced it out on the internet and costs were similarly high. I went to a fabric place and bought foam and did it myself. It cost about $200 and was definitely a modest improvement, at least in terms of looks. But after a few months, my husband offered to spring for a new sofa. Just arrived a few weeks ago, and it's a huge improvement.