If you have conchs and other obvious disease / damage on those trees, they're rotten and will fall - the only question is when. When will probably be the next big wind storm we get....or the one after that. So, how often do those happen Poppi (not knowing EXACTLY where you are here in WA)? In the Seattle area, it seems to be about every 5-10 years or so.
And with what you describe as to the typical size (30", 100+ feet tall) I'm not surprised you have so many that need to be taken down - that tall, in a mature stand there will be lots that could reach your home. I'll also say that anything short of a concrete blockhouse in the way of those things when they come down (at that size) will be absolutely destroyed.
As I've said in other threads, I'm a backpacker, so I get out in the woods here in Washington a lot. I see what Nature does to the hiking trails with every puff of wind that comes up. The first thing that has to be done every spring / summer is saw teams have to cut out the trees that came down over the trails over winter. Every....stinking....year.
Poppi - I'd suggest that you recall the winter before last, where 2 people were killed by falling trees on Highway 2 east of Stevens Pass when that ice / snow event hit before the ground froze. Lots of trees came down in that - areas I hiked not far north of Hwy 2 had jackstraw piles of trees that came down, uprooted and broken, many with no obvious signs of being diseased. I suspect the diseased trees started chain reactions - they hit their healthy neighbors, that were just hanging on, and dominoed down piles of trees. Hiking those same areas a few weeks ago, looking at the logs cut off the trails, many of them look totally solid.
One more thing - I was in a home that was hit by a falling tree, many, many, MANY years ago. Top broke off in a windstorm and landed on the roof over the kitchen. It only punched a hole in the kitchen wall where the trunk broke at the edge of the roof (one piece ended on the roof, the other piece slashed down through the exterior wall, knocking all the cabinets around.) Missed the pipes to the sink by 2", else it would have been a total disaster with water damage. That piece was only 12-ish inches in diameter and didn't fall too far vertically. I can only imagine how bad the devastation would have been had that tree been a 30 incher.
TL / DR - I'd get the diseased trees removed as soon as practical. They're coming down, the only question is when - when you choose it to happen, or when it's chosen for you, likely during a big wind, snow or ice event. It may be that you can only afford to have it done in stages, but I'd start with the highest risk ones first.
I'd keep shopping around on the price. Note that one reason it may be so high on the quotes you've received is that they're planning on taking them down in chunks, instead of "felling" them whole. Ask for clarification as to their intended process and inquire as to why they might not just fell them whole. Note that they may be too diseased to fell whole safely - if there isn't good holding wood for the hinge (cut the notch on the one side, then the back side cut a bit above the bottom of the notch, leaving a "hinge" of good wood that aids in directing / controlling the fall) things can be extremely dangerous to fall. An experienced feller will do a vertical cut with the nose of the chain saw (e.g. boring) a smidge above the proposed hinge to see what the chips look like (good wood, or rotten punky shit that will come apart).