I was wondering the same just a few days ago as I found myself out of my favorite menthol juice... The maker is based out of the UK and the US stockist for his juices has been out for months now with no replenish in sight...
Price of a 30ml bottle by the maker: $22
I like this particular juice at 24mg and a 50/50 mix.
So I went and did some research... Found all I needed at Wizard Labs
- Menthol Eucalyptus flavor concentrate by LorAnn (30ml): $5.45
- Menthol crystals (15 grams): $2.89
- USP PG (120ml): $3.19
- USP VG (120ml): $3.19
- Nicotine Solution - 48mg (120ml) - PG base: $9.99
- Nicotine Solution - 48mg (120ml) - VB base: $9.99
That totals out at $34.70 (give or take a couple bucks for S&H)... Let's say $40 all in.
Total volume of liquid purchased is 510ml. Let's say it takes me a few tries to get the mix right... Chalk 30ml down the toliet for testing and we're at 480ml of final product.
That's just over $0.08 per ml. So; yeah... I'm going DIY for this particular flavor.
Take the menthol crystals listed above and drop them in a 30ml bottle. Add about 15ml of PG - that will fill the bottle up. Shake madly til most of the crystals dissolve. then run a sink full of hot tap water and drop the bottle in there. take it out in about 10 minutes and continue to shake until the crystals are all dissolved. Drop it back in and let it sit until the water reaches room temperature. The menthol won't re-crystalize and it will be what I call XXX Menthol - be very careful not to get this in your eyes. To make your own you only need to add .3-.6 ml (1-2%) to a 30 ml bottle of juice for a nice smooth menthol.
So I got my shipment of goods form WL today and ran a test batch.
Went for a 4ml tester on the first try just to get a feel for the flavor.
Base Nic Level: 36mg - 100% VG
Target Mix: 18mg - 50/50 PG/VG
- Nic Base: 50% = 2ml
- Pure PG: 40% = 1.6ml
- XXX Menthol (PG): 5% = 0.2ml -
I hope you don't mind me "borrowing" the name dhood. 
... And thanks for the tip on melting the crystals. Worked like a charm and now I have 30ml of bottled "frostbite". Them crystals are fierce!
- Menthol Eucalyptus Concentrate (PG): 5% = 0.2ml
I added the liquids to a 4ml glass tester bottle and let the bottle sit in warm water for a few minutes. Took it out, gave it a good shake and dunked it in warm water for another "bath".
Once the mix reached room temperature; I dripped a bit into my tester atty and gave it a vape. Boy oh boy... was I pleasantly surprised. It's not quite at the level of "frostiness" that I am after, but it is a damn good start.
I scaled it up to a 60ml bottle and rand the process again. Same result as with the small batch... I'm going to take some juice out of that bottle to vape it as is (gotta get that fix!!!) and will the rest have a good steep for a couple weeks to see how the flavor matures. I'm hoping the eucalyptus grows a bit into the juice as right now it is a bit on the tame side.
All in all... Great first foray into DIY... Can't wait to get some more supplies so I can experiment with other flavor profiles I have in mind.
I think I'm going to like this whole DIY stuff quite a bit... Not giving up on purchasing pre-made all the way, but DIY is here to stay.
Thanks again dhood for the tip on melting the crystals.