I too had $3500-4000 for estimates so I decided to do them myself... I'd done the upholstery for my two cars earlier so I had some skills going into this... the upholstery on the sailboat was much, much easier to work on... I bought all the materials and extra foam for less than $300 and with the sewing machine in the boat I took apart the old cushions using them as patterns and made new ones discarding the metal zippers and using velcro as there is no chance of rusting the zippers (I could have gone with nylon zippers but the cost was astronomical
The foam was cut with nicro-thermo wire strung between two wooden studs... as the wire heated the foam was run through allowing 1-2 inches of foam to be removed (clean and sharp cutting like a hot knife on butter) and the new lower density foam adhesively bonded to the high density foam... then the polyester batting bonded to the lower density foam... worked great... in the v-berth I made a sunbrella cover with elastic band that covers the cotton duck in the entire v-birth. Vinyl is also under the sunbrella to prevent water from going into the v-birth cushions and keeps them dry when we store our wet sails in there... otherwise the v-birth cushions will need to be removed and allowed to dry... and who has that time?
It looks like a new boat inside and the color combination and softness of the cushions is like no other.... worth doing the different density foam.
Now tackling the teak and holly sole... darn varnishing!