Should there be a limit to how high a price on GTN can go?

No - price controls do not work.

Also for relics the issue of really high prices is driven by several things, all of which are controlled or constructed by Bioware, not the player.

First, relics are rare compared to say armoring mods, and the best come from drops and cannot be bought with commendations. This limits the supply of relics available to RE.

Second, relics cannot be sent to alts using legacy gear, so the artificer character doing the RE needs to actually run the content and receive the drops.

Third, getting a crit when crafting a relic returns an augment slot worth about 90K at best, as opposed to getting a second copy worth several million when getting a crit on crafting a mod.

If Bioware wanted to reduce the prices of crafted relics, they could make them less rare, allow them to be moved among a legacy, and / or allow a crit to create a second copy.

Any and all changes of which would be much better than trying to impose price controls on the GTN.

Yes, only to one person, not the other (lets say 9) people that came b4 him they was gonna pay 10 and only 10. Because a Collector would pay anything to add to his collection.
Now you see?

Absolutely not. Items are worth what the market will pay. Price fixing should not occur.
How are you making generalizations about "2.7 prices"??? You posted this less than 36 hours after 2.7 was released. Pretty early to make generalizations about 2.7 prices. These relics just became able to be RE'ed. The first people to list items always way overprice them (happens every time a new CM pack is released). On the Harbinger server now, I see several of those relics for sale around 4.5 million.
You're contradicting yourself there. If they could be obtained cheaply, then they wouldn't be selling for 5 million on the GTN. The only dye modules that can be directly obtained off the CM are usually only available for about a day and they are typically 600 cartel coins or more. I wouldn't call that cheap for one consumable dye module. But it's the fact that they have limited availability and, therefore, there is limited supply which is the factor driving their price.

You want the government (BioWare) to force a cap on prices for Rolexes (Relics) so that you can afford it, because you are too cheap and or lazy to actually work for one. If 25 million isn't a reasonable price, then no one will pay it and the price will come down on its own. Relics are not life or death items, like food or clothing, they are luxury items, so yes, you are selfish for wanting to force players to sell you stuff at an artificially lowered price.

When did the GTN start having a pricing ceiling? Never? When did the GTN ever have a pricing floor? Never?

If people are dumb enough to pay that price, so be it. It's the same with that Tauntaun. if an idiot wants to pay 3k in cartel coins for a mount, the demand will always be there

This thread is funny

...but my long answer was longer!!!

There used to be a limit (kind of) when the deposit was coupled to the listed price instead of the item's vendor value. That way you had to be able to "afford" to list for high prices and it also limited the number of items that could be listed for that high price. The outrageous prices on GTN started to grow in number and actual amount when the deposit was decoupled from the listed price. Personally, I didn't like it, but I guess it was a necessary move for the cartel market to be "successful". And I suspect for that very same reason there won't ever be a limit on how high prices can go.

As soon as you put a limit on how high prices on GTN can go, the really expensive things will only be sold on the fleet in the tradechannel