Before farmed pearls, the oysters had to be found and harvested in the wild (and few actually had a pearl inside) which made them rare. Because of the rarity, finding a matching set, especially a full necklace's worth, was difficult, time consuming, and therefore an extreme luxury.
Oysters can now be farmed, plus intentionally adding an irritant as a "seed" can make sure a large number of pearls can be harvested. Automated grading also reduces the labor/time costs for finding matching sets.
TV. You can get a cheap used old one for like twenty bucks where as it was very expensive once
One megabyte of RAM:
* 1957: $411 million
* 1980: $6,480
* 1990: $106
* 2000: $1.56
* 2010: ~ $0.02
* Dec 2017: ~ $0.0071
Pepper and spices in general used to be worth more than their weight in gold (quality saffron still is, I think).
Pineapples, [back in the day you could rent a pineapple](https://www.foodbeast.com/news/til-people-used-to-rent-pineapples/) to show off at your dinner banquet but they were too expensive for the average person to purchase.
Today they are available in every supermarket and relatively cheap.
Cotton. Before the cotton gin, cotton was so expensive to process by hand that it would be unthinkable to use it to make common, cheap clothing like underwear. Linen from flax was the everyday plant fiber prior to the 19th century.
There came a time around the 1830s where the price of cotton dropped so much that the wealthy stopped wearing it. It became a sign of wealth to continue wearing linen instead. This is also around the same time that you start to see rugged clothing made from cotton, like blue jeans. Before that, cotton was too expensive for work wear.
Knowledge. When I was growing up, a set of encyclopedias could easily cost more than £1000, so they were only for the rich or really dedicated parents. Then Microsoft Encarta happened, and the bottom fell out of the encyclopedia market, and now with Wikipedia and the internet as a whole no-one needs to pay a penny.
Computers. Where I used to work, there was a receipt framed for an Apple Lisa. $5600
My first boyfriend had a cellular phone in 1989. He paid $2,500 for the phone itself and it was $2 a minute for calls.
Calculators. Back in the 70s I worked for a guy who had a fancy scientific calculator worth a couple hundred dollars. He wouldn't let anyone else touch it. The rest of us were reliant on the old fashioned adding machines.
Back in the olden days, people used to use a candle - which would normally burn out every night. They used to get a new candle every single night, which as you might imagine can be quite resource-heavy.
Now, however, we can get LEDs with the same brightness for less than 10 dollars that could last practically forever and it only uses ~10-15 watts of electricity, which is really cheap.
Used to be an investment or a major purchase
A couple hundred years ago it was a luxury only available to the rich, Now over a hundred million tons are produced each year and it is so cheap it is sometimes used to bulk out cheap foods to make them cheaper.
Chickens, and eggs.
Chickens only used to lay 80/120 eggs a year.
Their meat was only eaten on very special occasions.
Most of them died during winter because they can't deal with no vitamin D, it's discovery led to a huge revolution.
From super fancy food, to the very cheapest.
The color purple/indigo.
Have you ever heard that purple is a royal color? That is because before cheap artificial dyes became available, thousands of [mollusks] (https://en.wikipedia.org/wiki/Muricidae#Historical_value) would have to be collected, pulverized and processed to create just a gram of purple dye, a process which only royalty/very wealthy could afford.
In the same vein as memory/storage, USB sticks. 5, 10, 15GB USB sticks are basically given away now when they used to be wildly expensive.
A day laborer today in developed countries can enjoy luxuries that only kings and queens could expect just a few hundred years ago, as well as some things that are everyday and boring to us, but that rulers would literally have waged wars to gain access to.
I used to do day labor to fill in between full time and regular work when I was younger. Get up before the sun was up. Go somewhere I was told to. Pick up rocks or bricks or wood or dirt and move them somewhere else until the middle of the day. Take a short break. Usually get given a box lunch. Do the same thing for a few more hours after the break. Get paid.
Same thing people have been doing for thousands and thousands of years. Some differences though. Safety, clean water, and the amount of pay and what it could buy. This was years ago when I did it, but after the labor company fee and taxes, I'd normally get about $80 for a day.
What could I get for that? A hotel room that could be cold in the summer and hot in the winter. That had both entertainment and news from around the world. Hot and cold clean running water. Flush toilets. Shampoos and soaps and toothpaste and floss provided with it. A device I could use to instantly communicate with people anywhere in the world, and enough money left over to use it.
Even after all that, I could afford to buy sweets or pastries from around the world. Fish from hundreds of miles away. Fresh fruits and vegetables no matter what the season was.
I could buy books. Multiple books! Just with leftover change.
Even something so mundane to us now...if I had a normal, simple headache or stomach ache or heartburn I could cure it cheaply and reliably in minutes without worrying about poisoning myself.
**Video calling**, especially international video calls which, historically, would have required dedicated satelllite access.
Now I just hit FaceTime or Skype and video calls are essentially free along with what i pay for my chosen phone and ISP.
Books. I seem to remember my history professor saying that before printing, books could cost about as much as a house
Microwaves. Things used to be over a $1000 in the 70's. That's like $1500 today. Now you can buy a small one for $25 at home Depot