Yeah, I don't really agree with the complaints on pricing in this game or inability to buy specific cards. Let's look at an economy breakdown on this thing:
$100 nets you 20000 gems, which translates to $10/2000 gems or $1/200 gems.
The cheapest packs you can buy are three packs for 600 gems, which nets you 24 cards for the cost of $3, including 3 rares. If you buy 6 packs for 1200 gems, you get 7 rares(6 in packs plus a wildcard) for $6. A single pack at the store may be $3.99 or $4.99 with 15 cards and a single rare, unless you luck out on a foil card. Buying singles on the other hand, a single rare dual land in the physical card game at a singles store/online will run $6-10, upwards of $15 for dual lands that are blue, which you can wildcard up plus have 6 extra rares for the same price in this game, along with 42 other commons and uncommons. I don't remember the mythic WC rate (30 packs maybe? Which would translate to 6000 gems or $30, which is price gougingly high for a janky phoenix, but roughly on par with top end planeswalkers at $20-25, plus you get 25-30 other rares and 0-5 other mythics to join the party.
Looking at the limited prices, Core 2019 is currently 750 gems($3.75 for 3 packs), competitive Guilds is 1500 gems($7.50 for 3 packs, dropping to 750 gems on the 11th of October), and Guilds sealed is 2000 gems($10 for 6 packs). The limited formats aren't "Arena Packs" of 8 cards, they are just like the physical ones of 15 cards, so you're getting upwards of 6 packs for $10, plus a rare wildcard of your choice(potentially $10+ in value on its own), along with all the other stuff in your draft/sealed pool. Compared to a physical purchase of 6 boosters for a sealed event, you'll be looking at $24-$30+ dollars at the store, plus taxes. The game maxes out at 4 copies of each card, after which they contribute to a magical vault algorithm which will eventually give you more wildcards to pick whatever you want with.
I haven't run all the numbers to figure out the exact specifics on price for building a tier one standard deck using only wildcards, but unless it runs like 12 planeswalkers there is a decent chance that you are financially way further ahead here than in paper, potentially even like half price or better?
Now, is the video game version as "worth it" as owning a physical card that you can turn around and sell in the future? Or that you can trade to the person across the table for that one rare you really need? Of course it isn't. Is the experience of sitting behind you're computer screen the same as sitting across the table from someone who's holding their cards and trying to disguise the disappointing fact they just hit their third land draw in a row? Absolutely not. But if you're someone who hasn't played a game of physical magic in ages and you just want to play a few games at 11 at night because you're bored, then Arena is potentially a very cost effective way to do this.
I personally think the asking price is super reasonable, but I also don't bat an eye at paying $20 for an expansion in Total Warhammer for a new race because a box of say 10 space marines or 20 goblins is going to cost more than that at a Games Workshop, and is not even close to a playable amount of pieces for the tabletop game. Arena is a way better approximation of MTG than Total Warhammer is of the tabletop game, so it's even more value to me in approximating that feeling/experience.
It all depends on the value you place ina digital product, but the fact that WOTC is offering this stuff at about a 1/3 discount compared to the physical cards seems like a reasonable ask to me.