Before you spend money on or rely on an appraisal, let's look at what an appraiser will see.
Appraisers today are more heavily weighting 3 mo activity vs. the traditional 6 mos.. They like the comps to be within 1 mile. They will stretch the 3 mo to 6 mo before they stretch the mile.
Given that criteria, the most notable comp is:
1) 19504 NE 143rd St that sold for $1,000,000 on 4/17/09.
The other 4 properties sold within a mile in the last 3 months only one would be considered a possible comp with adjustments, and that is:
2) 18021 NE 130th Ct Redmond, WA 98052 sold for $785,000 very recently on 5/5/09.
I know it's Redmond vs. Woodinville, but the subject property is less than a mile from the change from Woodinville to Redmond, so let's put this in as a comp.
Let's go out six months to find a 3rd comp, but keep in mind that the above 2 within 3 months may be more heavily weighted by an appraiser.
Nada. Not surprising necessarily, but now we only have two comps in 6 months, both in the last 3 months.
I like to look at assessed values. I prefer using 2008 vs. 2009 for my clients, but that takes a lot longer...so let's use 2009 for this Trulia Questions response purpose.
Comp #1 is assessed at $1,034,000 and sold for $1,000,000 (.967) - based on my previous studies, an expected result for an excellent property. Note that much like the subject property, this house sold in 28 days, but was listed at a higher price last season without success. Master bath was dated, but kitchen was updated. It is in The Crossings at Bear/Cottage Creek.
Comp #2 assessed at $925,000 sold for $785,000 - (.848). Main difference appears to be the kitchen was not as updated. There are several other interior features that were quite popular back when the home was built (same year as comp 1) but are not popular today. Moreso than comp 1. It is in Highgrove at English Hill.
Subject property assessed at $870,000. The fact that it was built in 98 vs. 89 does not seem to be too much of an advantage, as they used the wood trimmed countertop more popular in the early to mid nineties, and the white cabinet scheme with short vs. 42" cabinetry (from what I can see in the photos). The master bath had gold trim, a carry over from the late 80's and early 90's. There appears to be less detail work at time of construction. No tray ceilings. A medallion insert vs more expensive craftsmanship in the two comp properties.
Without going into a lot of detail, suffice it to say the range is set by the comps at between .967 and .848 of it's assessed value of $870,000 which would give you a range of value of $841,290 on the high side and $738,324 on the low side.
The wild card is the third comp. The appraiser will use a 3rd comp and whether he will stretch area out from 1 mile or time back from 6 mos...usually he'll go out from the mile, but weight it on the light side. The scary one is 20907 NE 156th St Woodinville, WA 98072 built in the same year as the subject property. There are many he can pick from depending whether he wants to push the value up or down. If he uses that comp, it's a $1M assessed that sold for $645,000. It was "bank-owned", and I have seen appraisers in that area pulling in a distressed sale to tone down the value for added lender protection (if it is an appraiser ordered by the buyer's lender). I've seen this twice in Woodinville/English Hill in recent history...so it's a strong possible unless you have substantial cash down (in excess of 40%)
All things considered, I'd say it's a scary one to approach off market. If it were a listed property, you might have the advantage of using a reverse escalation clause, and bouncing off another bona-fide offer.
My $.02 FWIW