We bought Ikea cabinets after doing a huge amount of research. While doing that we also looked at the countertops that they had there. They gave us a referral sheet to contact their contractor and we went to select a stone. The quote that we got was very high. We ended up using another fabricator who was just over half the price that we would have paid to Ikea. This is not to denigrate the value of Ikea's warranty, etc. but there are a lot of good fabricators out there. When you buy through Ikea you are paying the fabircator's price, plus Ikea's markup. That money could go towards something else.

Love love love this topic. Your kitchens are amazing. Looking for pics of stainless; particularly of stainless with white cabinets and beadboard backsplash... Have you ever seen this combo? Any ideas would be awesome. Again truly amazing kitchens!!

"My question is: should the 30mm thick quartz countertop be able to support its own weight over a 30 inch span without sagging?" No, look up your quartz manufacturer's recommendations. It shouldn't be too big a deal to fabricate and install some inconspicuous angled metal support.

I just renoed a similar size home. Put new cabs with granite. No laundry though. $9k for remnants and chinese cabs. My last laundry room was $1k for ikea and laminate (probably less actually). Base budget for current build is $35k. A bit more square footage but it would scale down to $28k for you. So my suggested range is $10k to $28k. Helpful? probably not but really the best I can do. Add 20% for HCOLA. What you can do from plans is get linear feet of cabs. That helps. Island? Paint vs stain? Crown/end panels etc? Custom panels for appliances? Ceiling height and plan for uppers (stacked/tall uppers etc). But most importantly is expectation on door complexity and degree of customization.