here is some real world costing comparisons
I received an estimate for my boat to take care of the exterior gel, including the spider cracks, a bit of fairing, re-texture the non-skid, etc. that was $6k - $10k if I had them sand off the bottom paint. to do the cockpit was another $4k. that was all cosmetic. I did it for lots of sweat, and about $1000 in materials.
I had to fix the transom and stringers on my Avanti, I took it to a marina that specializes in fiberglass work back in 2006. the guy pointed me to this forum and said, "it would cost you 4X what the boat is worth in our shop". the quote was $10k to do stringers, floor and transom. I did it for about $2200
your rinker with a soft floor will need stringers, floor, transom, foam, etc. just the materials, supplies, incidentals alone to do it right will be $2-$3000. then about 400-500 hours of work. granted a good shop can probably do it in about 120-150 hours as they have experience, shop room and cadence...... and they buy the materials for less, however they dont sell them to you for less......so using $120 per hour for 150 hours..... thats a labor bill potentially of $18000 to do it right
now, lets look at what they may do. they will cut every corner to get your floor out, new stringers in and a transom in. as Ted mentioned, the bill will be about $10k they literally will use a sawz-all and a chain saw, cut out the bad, do minimal grinding, lay the wood in, tab only the minimum, pour in foam, hose it down with bilgekote and glue the carpet in.
most people wouldnt pay $10,000 to $20,000 to restore an old boat when you can buy a much newer boat for that
and you still have an old rinker. that is why most shops do not want to take on the work unless you pay them up front.