Is it common for tubes to outweigh the cost of the amp or preamp?

One way to save a few $$ is to buy ugly tubes and pairs and quads that were all manufactured the same but we're labeled for various companies.Sometimes a couple of new production tubes alongside of a couple of NOS sounds good too.

I don’t know about that but I did spend more on Herbies Tube Dampers than I did on tubes. 

samiamnot-

No insult intended with my post. 

The intention was to raise awareness  that perhaps one might consider  starting with a substantial "box" before additional expense-especially if it exceeds the value of the actual box.

I use tubes in my system-amp,tuner and phono. Using NOS tubes that cost more than the equipment, won't ensure anything. Since it's a headphone amp, I would be more concerned using QUIET tubes. 

If you do find it improves your experience, that's all that matters. It's all subjective, YMMV and all that.

Considering tubes that cost more than the equipment, would be a reason to reevaluate my original purchase, and perhaps upgrade to a better unit.

VERY common .

That doesn't sound like a good investment. 

Changing tubes can have a positive effect on the sound or it may sound worse.  Or those expensive tubes might go microphonic in a month or few. 

I personally have found tube rolling in different devices to make relatively small differences in the sound signature, much like cables.  To me, it's worth doing, but in moderation.

I would have been inclined to buy a better amp than to have spent that much on tubes for a relatively inexpensive amp.

The difference when tube rolling isn't typically revelatory, which is what I would want expect if I spent as much as you did relative to the cost of the amp. 

I don't know what headphone amp you purchased, but even if it was used and you got a great deal on it, you shouldn't expect too much for what you spent. 

I hope you have an option to return the tubes.  My guess is you're going to be disappointed.