The domino effect of a few 2006 property sales that have doubled some assessments and taxes in two West Tisbury neighborhoods are simply part of a trend toward sharply increasing values on waterfront and high-end properties, the town principal assessor said this week.

A number of Tisbury Great Pond and Seven Gates Farm homeowners are in the eye of the tax bill storm, while other West Tisbury tax bills have increased moderately, are unchanged or even lower than in 2007.

Principal tax assessor Kristina West said she understands the concern but sees no letup in the trend.

“Usually property values and taxes rise or fall townwide in a very similar pattern, unless there is an abnormally high change in value in a particular neighborhood. That is what happened this year on the Great Pond and at Seven Gates,” Ms. West said, pointing to three large 2006 sales on the Great Pond in which properties assessed at about $10 million sold for more than $25 million combined.

“We’re seeing a lot of middle and low end values not going up but higher properties values are going up. We’re seeing more of these sales. At some point, those prices become the market value,” she said, noting that a property on Priesters Pond sold recently for $15 million with an assessment of under $10 million. “We have to generate valuations based on fair market value. Everything is a function of market values,” she said.

Last Thursday night, 24 of the affected taxpayers met at the Howes House to plan 2008 tax relief strategy. They began with a tutorial on the tax abatement process led by residents Joan Ames and Jonathan Revere. The group may meet again after the outcome of their abatement requests are known. Fifteen abatement requests have been filed but the town expects the final number may reach 100 by next Friday, the deadline for filing.

Some taxpayers believe the high sales are anomalous and in at least one case, may not meet the arm’s length sale standards required for inclusion in setting valuations. But Ms. West disputed the claim. “We have no evidence, based on information available to us, that these properties were not sold at full and fair market value. Rumor is not one of the things that disqualify a sale for inclusion in value-setting,” she said.

Abatements must be filed at town hall or postmarked by 5 p.m. on Feb. 1. Abatement forms are available at the town hall.

Ms. West cautioned against focusing solely on the sale of the Drexler property at the tip of Middle Point Cove as the sole cause of the spike in assessments. (Three Drexler parcels, assessed at $6.8 million, sold for $19.6 million in 2006). “In fact, several other sales contributed to the reassessment,” she said.

Total valuations in West Tisbury for 2007 were $2.71 billion, up 10.6 per cent from $2.45 billion in 2006. The town must raise $11.1 million in taxes in 2008, an increase of $287,000 or 9.5 per cent from 2007.

The town contracts with Vision Appraisal Technology in Northboro for its assessment work.

Vision’s methods came under scrutiny last year in the Graham tax case, which remains pending in the Massachusetts Court of Appeals. William W. Graham, who owns a large property at Mohu, has challenged his tax assessments in a complicated case that was the subject of the longest-running trial in the history of the Massachusetts Appellate Tax Board. The tax board ruled in favor of the town and Mr. Graham is appealing. Briefs have been filed on both sides; a date has not been set yet for arguments.