In the US, you can expect to be paying between 50 and 100 dollars for a 20mL vial of testosterone, concentrated at 250mg/mL. Most compounds will be priced similarly. Tren would be about double this amount (you could pay 100 dollars for 10mL, for instance). Let's say 2 dollars per day of an oral, any oral. There's variation, but not huge variation.
A strong first cycle would be 12 weeks of testosterone at 750mg/week, 6 weeks of d bol at 50mg/day, and I'll add in 20 dollars worth of arimidex as your AI. The math on this ends up being between 200 and 250 dollars, approximately, for the entire 3 month cycle. And that would be a very nice cycle. So about 70 bucks a month.
A cycle that I would consider to be quite strong, but not insane, would be 1g of testosterone, 500mg of tren, and, say, 500mg EQ, for 12 weeks. I'll also throw in an oral for the entire duration of the cycle. I'll triple your AI dose. This ends up being 550ish dollars for the cycle, so 180 or so per month, assuming you get good pricing.
Things that can be added on to cycles would be peptides, insulin, GH, etc. Insulin is cheap, peptides are similarly priced to steroids generally, and GH has an enormous range, depending on sourcing, but will add several hundred dollars per month at least.
I would say Ross's estimates are on the higher end, but of course it all depends on sourcing.
If you want to shoot for world records, you could potentially spend 5000 dollars a month on drugs or more. This could include something like 2g test, 1g tren, 1 g masteron, 1 g EQ, insulin, GH, an array of peptides, and half a dozen orals (d bol, anadrol, methyltren, anavar, etc)