I still don't think so.
DS I deal with has 2 compressors. He pick them up from shops that went out of business. So $15K is probably not a bad figure for a smart shop. Amortizing it over 5 years may be OK for tax purposes but the life of a good compressor, with proper maintenance, is probably much better than that. Overall, your $5K annual cost for a smaller LDS fill operation does not seem unreasonable. But who is only doing 1000 fills per year. Even for a smaller shop, something on the order of 2000 to 3000 fills per year seems more reasonable. (Hell, just my buddy & I account for about 100 fills per year.) Now my fills estimate includes the fills on tanks provided for training and training support, rental tank fills, and fills of privately owned tanks. So it still looks to me like you would have a hard time working up a cost per fill much more than $2 to $3.
I just don't think you can get over $5 cost per fill unless you are only counting fills of private tanks and ignoring training and training support fills and maybe even rental tank fills. Or you are looking at a really inefficient operation, the kind that we might all be better off without. And if $10 per fill cost is right, the DEA should be raiding that shop.