Custom = slow if you aren't making a whole hell of a lot IRL.
You may have to make sacrifices on both ends, what you want and what you have already that you need to give up in order to make it happen.
Compromise is a friend until it starts costing more in oversights, and obviously you're considering backpeddling on the important things you were after in the first place.
Nobody makes an omelet without cracking open a few eggs first.
Knowing exactly what you want or thereabouts helps motivate, and give a direction (helps avoid needless spending to some extent), but your own determination of what you want may still be far out of reach.
First estimation is never accurate unless you're going by someone else's recipie–then it isn't really custom so much as copying someone else's idea. If you do the latter try to at least be sure they knew what they were doing; if you trailblaze you stand to learn the most because you will be involved in every aspect of the entire process from start to finish (as it should be).
The end result should be greater than the sum of parts because it is a learning experience (as is life).
