Thanks for the referral! They are currently $14.09, which is pretty darn cheap. Give or take a few cents, that should be about the lowest price around right now (I check weekly on pricing). Here is the link:
The short story is that independent research points to the ZooMed Reptisun 5.0 linear product line as having a better combination of longevity, UVB1/UVB2 ratio, general UVB uW/cm2 levels, ZooMed is located in California with easy phone support, ZooMed representative are at major reptile shows to answer questions, and yet the product still found with excellent pricing at places like LLL .
By the way, unless you have a really big need for the little 15" tube, I'd stick with the 18" tube instead since it is much more common to find and so is the fixture.
As a company who sells both brands, take my word for it - Zoo Med reptisun 5.0 bulbs are miles ahead. The repti glos are ok, but the reptisun 5.0's are well worth the extra few bucks. I have been inside Zoo Med's research area in their facility, and have seen every brand of light bulb set up, running, and being tested. They really do put in the time and effort into their products!
As for the lowest price, actually, I found them for $13.96 last night after I made the post (13 cents cheaper than us. LOL). Like I said, give or take a few cents, this is the cheapest price around right now. Hope this info helps!