Below are a few examples of LED coasters that are commercially available. In addition to these, there are a handful that can be found on 

FlashyBlinkyLights Infinity LED Coaster

https://www.flashingblinkylights.com/infinity-tunnel-led-coaster-sku-no-11051.html

Cost for one: $5.30 CAD (price breaks available on higher qty)

Device uses two CR2032 batteries (included). Price is good, but the major cost over a long period of time would be the batteries themselves unless those too are bought in bulk. It isn't described how long this can go until battery replacement is required, but likely multiple times a week. Coaster height not advertised.

FlashyBlinkyLights Pressure Activated LED Coaster

https://www.flashingblinkylights.com/light-up-products/light-up-bar-items/led-bar-supplies/light-up-coasters-bar-trays/square-light-up-drink-coasters-color-change-led.html

Cost for one: $5.30 CAD (price breaks available on higher qty)

This is a pressure activated LED coaster. Device uses two CR2032 batteries (included). Price is good, but the major cost over a long period of time would be the batteries themselves unless those too are bought in bulk. It isn't described how long this can go until battery replacement is required, but likely multiple times a week if used regularly. Coaster height not advertised.

Glow Products LED Coaster

https://glowproducts.com/ca/multibigbasecoaster?___store=ca&__from_store=ca

Cost for one: $2.90 CAD (minimum qty of 6 required)

Another pressure activated LED coaster. Device uses 3 AAA batteries (not included). 24hr of continual use between battery changes. There would be a large cost in batteries for regular use. 20mm coaster height.

Brag Gear Retro Lights LED Coaster

https://braggear.com/products/retro-lights-led-coaster

Cost for one: $19.99 CAD (price breaks available on higher qty). 

Device uses two CR2032 batteries (included). Battery life likely below 24hr. 4mm coaster height.

Conclusions:

Most LED coasters out there are quite cheap when you don't consider battery purchases. Regular commercial use of these coasters would add up in price and environmental impact with regular replacement of multiple batteries per coasters.

A smaller number of coasters out there have direct DC power connections or include a USB port for charging a rechargeable battery.

From my search, there does not appear to be any LED coasters out there (commercially available at least) that are either wirelessly charged, or uses capacitors for energy storage rather than traditional batteries. The following benefits of my design may be enough to justify a higher price point:

1. Easy wireless charging.
2. No continual battery purchases. Smaller environmental impact as there will be no batteries or battery packaging that will end up in a landfill.
3. Hardier design than competitors (fully sealed and protected from moisture).
4. Aesthetic design displaying circuitry.

I will be reworking my BOM pricing based on buying parts in bulk, and some redesigning to be able to use less supercaps. The the project log will go over the cost to manufacture and a possible sell price to compare to existing coasters.