For something where mats cost 1000g I wouldn't tip by %, they'd probably get in the neighborhood of a 25g tip from me in most cases.
Generally most enchants will get a 10g-15g tip, maybe as high as 20g if they come to me. I would never use a crafter's mats, with the exception of nethers under the old system which you payed for outright anyway.
Generally, I find that I get tipped around 100g for an epic gem cut if the person farmed it themself. If they bought it off the AH, they don't usually tip much higher than 50g. Given that I can sell a Solid Empyrean Sapphire for 800g within an hour and the raw gems sell for 300g or less, yea -- that's fair. It makes you hesitant to cut gems as a service though.. since even if they bought your raw gem you'd end up losing quite a bit of money, over 50% in some cases.
Enchants can't be crafted and then sold (yet) so this same raw mats vs. finished goods discrepency doesn't occur, and the enchant value really is the same as the mats involved. The enchanter doesn't lose money by selling raw mats and then performing the enchant (infact, he/she makes MORE money that way) so I think it's fair to tip enchanters well, but not nearly as high as a crafter that eats over 400g of lost profit just by performing the service rather than grociering.