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You are correct. If you are willing to wait about a month for delivery from Hong Kong, you can get 10 blue 12V T10 LEDs for $1 with nearly free shipping.
I have had pretty good luck with these and other similar bulbs.
This particular bulb is an exact match for the blue flasher in the train on my AC/DC premium.
ebay.com link: 10x Super Bright T10 12V 194 168 Blue LED Wedge Plate Dashboard Side Light Bulb

In the case of this blue flasher, it looks identical to what was originally installed, when I got the machine.
I think if you search there are many colors, sizes and options.
Note that T5 bases are a smaller size normally used on instrument panels and such, so they don't fit my pinball machine.
I got some for the cluster bulbs and dome lights on some vehicles I own.
And these are all 12V for automotive purposes, which would only be suitable for flasher bulbs.
There are others available at 6.3V which work for GI applications, shown in the 2nd photo (in the red box).
There are a few flasher bulbs mixed in that box also.
They are all so cheap from China, I got quite a few in various colors and sizes that I thought I might need.
They are also available with bayonet bases if you need that configuration.
Only real drawback I see is delivery is normally about a month, so you have to be patient and order the right items.
So far, I haven't received any that didn't work.

12V Automotive Bulbs (resized).jpg

6.3V GI Bulbs (resized).jpg

Those smaller instrument panels bulbs, located on the cluster/instrument panel, can be replaced with a T5 LED.
Some vehicles have the larger T10 base, depending on the vehicle.
They can be purchased in various colors, white, blue, pink, red, green, etc, etc...
Some people call it an accent to make the dash display a different color.
Getting the cluster out of the dash is the hard part...
Replacing little wedge bulbs is easy, but you have to check polarity.
I personally wanted blue for my instrument panel, so I got blue T5 LEDs for the most part.
Incandescent bulbs I removed are in the photo below, small ones in the center.

Instrument Panel Bulbs (resized).jpg

1996 Ford Ranger... For the cluster and the temperature controls. I used a variety of LEDs.. Some flat, some domed. I used the ones that gave the most light for the area they were in.
Also added some in a 2000 Ford F150, but had to use white LEDs there, because there was green tint behind the cluster display that blue light would not penetrate. Mostly T10 on the Ranger and mostly T5 on the F150. Newer vehicles might not have the same type bulbs like mentioned before by others as some have circuit cards with SMDs mounted directly on them for the display now. Reminds me of those node cards on some newer machines. So, if you have a display problem on those newer vehicles, you probably have to get a new display at significant expense I would guess.

IMG_20170914_194326 (resized).jpg

IMG_20170914_194349 (resized).jpg