I have built a custom mountain bike with good components, how do i get it valued?

you can find out the cost of each individual component, but it's only worth what you can sell i for. Chances are that you won't get the money that you put into it. If you like it, keep it and enjoy it!

Adding up the cost of the components is one way. But What I did, in the case of my Daughters bike, was to sell the bike. Of course, it has a custom fiberglass frame that looks like a moped:
<>http://i134.photobucket.com/albums/q119/...
The cost to me was $270.00, but I sold the bike "$3,000.00 O.B.O. " (Or Best Offer), and I got $1,200.00 when I sold it. That's a profit of 450%.

This method is better than using the cost of materials, because it takes into account the artistic value of the bike.

(Sorry, I got a "code999 error" so you will have to copy and paste the link)

(Cost of components) + (cost of original bike)

Take that number and divide it by the amount of decades old it is.

If it's made of steel, divide that number again by 2.

If there is obvious wear and tear, divide that number again by 2.

man.it most be the **** i would like to see.

stick it on ebay and see what it retrieves, you can set the reserve really high if you dont want to sell it.

Being you built it you should know how much you have in it. Add it up and then compare it to what you see for sale that's about the same in quality. You can also ask a bike shop and there is always someone in a bike club who is up on the current market values.

This is tried tested and true, based on retail pricing vs. OEM pricing. I had to do this to work out import pricing on bikes I design.

1) Take the retail price of all your parts and divide by 5. This would be close to the factory cost of the bike.

2) Multiply this amount by 1.4. This is the approximate wholesale value.

3) Multiply again by 2.2. This is what your bike would sell for new, at retail pricing.

Of course, weird or "barely compatible" component choices will drop it's value as would it's age and condition. Just because you think it is cool doesn't mean others do... one of the big challenges in speccing new bikes.