You can find the cost of registering your tartan at www.tartansauthority.com. The cost of weaving will depend upon where you have it woven and in what quantity.

I can only speak for us at The Scottish Tartans Museum, but we offer custom tartan in wool with only a 4 yard minimum. Cost at that level is $65/yd (it is 29" wide), but if you are needing greater amounts the price can vary.