Need help on front to back heater hose replacement!

The hose itself is not that expensive. They must be quoting you to disassemble your chassis and replace the hoses EXACTLY as the originals are routed.
I would guess that new hoses could be routed in an easier location and secured to the existing frame for a lot less money, even if you use the far superior newer silicone heater hose material.
Get another quote and have the tech advise if there is another way to route the heater hoses to accomplish the same result.