Easier to be uber I think he compares with 70 pvp, and what it takes to be uber there. It is cheaper to be competitive in 20-30, though they really need to add dread gears to the drop table to make that work better. A good player in full or mainly dread gears, linked 6s (which aren't nearly the cost of link 7s) and armour  (easy to get with just lapisia), well rolled OJ, and high enchant weapons if DPS type can be easily competitive. Yes, if you want to be on the level of of total uber, leg all s etc... cost a good amount, but still, less then getting ROTCO, linking it 7s, max OJing, enchanting, etc.
Most dread gears run 10 op each...
5-10 op to link a piece, only non-DPS really should link abs, so 5/6s, link no hammer on bonus day.
10 lapisia to enchant to  or so
50 rec runes to get nice rolls.... if you pick, less if you just want good HP usually.
so, 30 op = good armour piece, less if you lucky way less if you healer or rec based
Weapons - dread of choice = 11 op
10-15 op to link more then armour because of the flash people like, link on bonus
50 rec runes to get nice rolls
enchant - cost depends on luck and choice, can use all GM enchant= about 62 op.... or can use lapisia, then add GM enchant, depends on your luck... but this is to get uber dread weapon.
50 op usual now for DPS linked accessories... if you buy pre-linked, again depends on luck if you good linker, can link way less, if you not better to buy.
But the biggest thing to remember is, Canta is user friendly usually, at least fury side. Come to Canta and play while you are working on gears. You don't have to be uber or even competitive day 1, just come and enjoy and get to know the players an have fun. If you love the people and the fun there, then put the time in. But even if you come in farmed heroics linked with duals and NPC accessories, if you come, and you try, and you show good attitude, you will be loved. Once you there, if you love, then get your gears and put work into them.
OK, so based on the numbers you threw out there (using your lower estimates where applicable) I ran some numbers to see what it would cost in USD to be "competetive" in Canta.
Dread armor, self rolled, 5 pieces= 150ops
Dread weapon, self rolled, all GM enchants= 76ops (152 if you want two different ele weapons)
Accessories x5= 250ops
This brings me to a total of 476ops (with one weapon.) Now, lets assume I'm buying OPs from the item mall, using their bulk discount package of 20ops. That package costs 16436ap. I will only need to purchase 24 of these bulk packages. Which would be a grand total of 394464 AP, or approximately $3944.00usd. Just under $4,000 to be competitive in a low-level zone in a free to play game.
*Edit* Just wanted to add one more bit: the community of regular canta PvPers are, for the most part, one of the friendliest, most "open" groups of players I've seen in-game. The majority of them really care about the health and balance of the zone and are very open and accepting of new players who are, as you said, in farmed/quest heroics and duals. I have never been kicked from a Canta raid for being undergeared. The community there is great, it's the cost to compete that is unbearable.
Now, disclaimer part: I understand that there are ways to work the tiers, recycle rebates, purchase AP cards in-game with OPs from recycled tiers, etc etc etc, and the actual dollar amount spent can be far lower than the above estimate. But for the most part, most of the cost reduction strategies require years of playing and accumulating wealth. Newer players don't have this luxury. Farming opportunities in-game are insufficient to support this kind of cost to compete, so the new players coming in see the how much others are "spending" and think "I'm out. Not spending thousands just to be able to enjoy PvP."