Players make a lot out of realm choice and focus quite a bit on the question: “Which realm should I pick?” While there are differences between realms, my personal experience has been that this will not make or break your ability to make gold.
What factors differs between realms?
We are all playing the same game in the same world. Mobs have the same loot tables, spawn timers and locations. The only difference from one realm to another is the people on it. The Auction House is purely composed of player actions, so differences between player base and type can lead to significant differences in behaviour.
Luckily we can boil parts of this down to some very simple factors to help focus in on the differences that matter and what you can know about them.
Competition and customers
There are two main groups of people whose behavior will have an impact on your ability to turn a profit, your competition and your customers. Luckily both groups tend to follow some trends based on some fairly easily accessible server data.
The big bucks are in performance enhancements
The best items to sell for gold are always items that yield some form of performance increase. Whether we are talking about perfect corrupted gear in BfA or Edgemaster’s Handguards these items sell for a huge premium as they are INCREDIBLY strong in end-game content. The more players care about end-game content the more gold they are willing to spend on this on average.
Which factors matter then
The main factor that matters a lot is the total population, although the effects are quite different between classic and BfA due to the sharding in BfA. Other factors that matter include the realm type, the hardcore raiding population and the PvP population.
BfA high population characteristics
High population in BfA usually leads to lower prices across the board. More items are generated and there are many more players selling any given items which tends to drive the price down. This is also the case for crafting professions where many more players will be trying to sell the item typically making crafting profits thin.
Higher population realms usually have significantly more hardcore players as well. These realms typically have tougher competition, with more hardcore AH campers.
On the positive side they have SIGNIFICANTLY more gold on them, and the gold totals you can reach are MUCH higher if you can find the right markets.
BfA Low population characteristics
Lower population means higher average prices and significantly less competition. You can more easily control markets and you don’t need to camp as much. You won’t reach the staggering heights of potential gold that you can make on a high pop realm, but it’s generally easier.
There’s obviously a sliding continuum between the two extremes.
High Population Classic
In Classic everyone shares the same game world. So on higher population realms anything that drops from the open world will usually be much more expensive than on lower population realms. The high pop realms typically have more raiders and more hardcore players than the lower ones, just as in classic.
Low population Classic realms
Lower population realms in Classic typically have lower prices across the board. Profit margins can be higher, but that’s not a necessity. Overall you will face less competition, but competition does not matter as much in classic as you can use stack sizing to still get sales without camping the AH relentlessly.
Realm Type
RP realms typically have less hardcore player bases. People who are attracted to the RP side of wow are usually more concerned with cosmetics and just enjoying the game rather than hypermaximizing performance. That being said even on RP realms you will usually make the majority of your gold from power increasing consumables.
How much does it matter?
The biggest impact it will have is really the difference in profitability of the various possible goldmaking methods. Figuring out exactly which crafting professions and which recipes work well on your realm is something you will always have to do.
Overall realm differences are more likely to impact you in BfA as competition is a much bigger nuisance on the 8.3 AH than the old one.
Personally I would never pick a realm to play on for goldmaking reasons. That being said my personaly playstyle has typically worked better on medium to low populations in retail, but it’s worked just fine on the highest population EU classic realm. There are always niches to use, so just get out there and find them!