In general, all other things being equal, refinishes will almost always sell for less than all-original basses of the same kind, no matter how professionally done.
It will hurt the price of high-cost, highly sought-after basses proportionally more than cheap basses. In other words, people care less about a refinish on a $250 used Squier than a $10,000 refinished Pre-CBS Fender. The refinish on a Pre-CBS Fender will take a much bigger hit in resale value. Where a Sadowsky MetroLine falls on that spectrum i don't know.
All that said, i'm kinda of the opinion of, who cares? Are you buying the bass to sell it? Or are you buying the bass to make music with it? If you want the bass and you want it a different color, get it and and have it painted and enjoy it. It's a musical instrument, not an appreciating asset class. The value of a bass isn't the dollar amount you can sell it for; the value of a bass is the music you make with it.