$38.99 – Medium temperature: -40 ~ 55 ℃, Maximum plateau slope: 10%/80V, Life: > 1x 10^9 pulse, Minimum plateau length: 80V, Name: Radiation system, Starting voltage: < 350V, Geiger tube parameters: , The maximum count rate: 25 times / min, Recommended operating voltage: 380V, Technical parameters diameter: Φ10±0.5mm, Extreme operating voltage: 550V, Total length: 90±2mm, Size: 108x63x20mm.
$38.99 – that is current price with coupon for Geekcreit Assembled Geiger Counter Module Miller Tube for Arduino (in Banggood). Check coupons or create price alert down below. What is best price?
Latest coupon and price update (UTC):
Banggood ($38.99)
Banggood warehouse is located in China. Hmmm… There is no active coupon in Banggood at this moment. Price? Well, this price is higher than average price ($34.99)
Link: Banggood product page
Price: $38.99
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGc7db29, Cuponation9, BG8ReviTrage, BGf6ca76, BGcoupon8off, BGGutscheine, TTBLACK5, BG589b2e, BG8FORMULAMX
(these coupons are old, so probably won’t work)
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Check out price history chart (for all/most countries) for Geekcreit Assembled Geiger Counter Module Miller Tube for Arduino. The lowest price was: $29.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).