First, for the want -
I had a bow thruster installed after I bought my used Marlin 3 years ago. Joe Molinaro at East Coast Bow Thruster installs Vetus thrusters and he and his team did a great job for several thousand less than what you mentioned. I had the Vetus BOW55 installed although Joe said the BOW45 would have been sufficient.
Now, for the need -
I'll admit having a bow thruster is nice. I use it when I need it but try not to rely on it. Many a day I'll make a conscious decision to NOT use it so I keep my skills sharp. You can, and should, learn to maneuver your boat without one. Having twins is a really nice thing. Many people do fine without a thruster and you can too. Practice, practice and more practice.
Last, for the nice-
On days when the wind is honking from from a troubling direction, a bump from the thruster can make things much easier. If I can, I will test it BEFORE I use intend to use it so I know it's working. You never know.... It can be helpful getting off the dock as much as on. For example, my boat is slipped east/west, facing west (close enough) tied starboard side. When the wind is blowing from the NNW/North/NNE, I know getting out of my slip will be a challenge before clipping my neighbors' boat on my port and getting my bow around to the right so I can head out. A bump or two as I'm pulling out, done, no worries. The alternative would have to be to turn to port, clear my neighbor and back out to the main road. Just sayin' there are alternatives. On days the wind is honking from the south, I'll back down my street from the main road so I have my stern to the wind. Much more control that way!
So, do you need it? NO
Is it nice to have? YES
Is it the answer to all your docking troubles? NO!!! You still need to learn the art of twins.
Is you wife giving you the OK to spend money on your boat? :dance