There is no right or wrong answer to this question. The problem with "custom vettes" is that often the one doing the custom work is Bubba. You know Bubba, he cuts and splices wire with duct tape, he does fiberglass and bodo repair with steel wool pads, he mixes laquers and enamels, and cuts corners at every opportunity. Also, many custom vettes became customs due to a severe collision, fire, water damage, theft recovery etc, where it was cheaper at the time to "customize" the car than put it back right. Look at the story behind yours in fact. It appears that the headlights have been smoothed over. The truth is that at one point in time the owner was either frustrated with inop stock units, or the car was hit. Rather than fixing the problem they went the route of doing away with them. This is not a bad thing, but one of the reasons they become "customs".
There are some customs out there that have been done right. I hope to put mine in that category when complete. That is well thought through, no cost spared, no stone overturned cars that are custom with a purpose. That is, they don't just look good but they drive and handle better than a stocker. Those bring money. The others are just half breeds or compromises due to budget, time, etc. We have all seen a custom vette that looked great going down the street, but was a rat hole on the inside. Or, a "numbers non matching" high horse power beast that looked like it was ready for the scrap heap on the outside. This is what most people think of when they hear custom, and automatically are not willing to spend as much as they would on an all original car.
In the end it is worth what you pay.
I don't think I would part for a peny under $50K when I finish mine. Would I ever get that? Who knows? Who really cares? Some people spend their money on booze, parties, golfing, sports, movies, collectables, etc, but you have choosen to pursue the Corvette legacy. Keep your receipts in the event the car is ever stollen or totalled out, but don't ever add them up! You never get back out of one what you put in, so enjoy the ride and welcome to the club.