Currently: Lighting maple logs to OSRS gold get from 67 to around 85 firemaking, just to train something, does not mean that I can't do anything else. Cash: Around 2.5m like I spent money to purchase bandos chest and bought 20k maple logs. All quest w/o getting over 1 Def, 50 Atk and 45 Prayer: Assuming you are 1 in the stats when you start...
I highly suggest you do any prayer based quests . If you begin prayer, you won't be good until higher combat (like 75 strength+). If you stay 1 prayer you can pk a lot earlier and help avoid that"all work and no play" problem which many pures do. This helps to keep most people inspired. You might even stop at 50 attack for granite mauling first. Stay legit man. 90 percent of pures (that's a made up statistic, but it is likely unfortunately accurate) nowadays are botted, combat brace sporting nubs.
In my explanation, I'm are assuming that you are getting 95 prayer from roughly 75ish. You are able to add in your own numbers and follow exactly what I did to see if its different. Therefore a 35m difference in the purchase price and also a 15 hour time difference. So if you value your own time at 2.3m+/hr it is worth it to use frost dragon bones. But this is assuming you have the money already, that you dont, but if you want to collect the frost bones to make this possible you can.
Now for the collecting the bones. It all is dependent upon how much you really make/hr. Should you create 2m/hr then it is 90 hours to the frost bones and 72.5 hours to your dragon bones. And you need to answer for yourself if 2.75 hours is worth 35m. Therefore it's better in cheap RS gold your case to utilize dragon bones, by 2.75 hours gap and 35m. Dragon bones are all about the same time as frost bones, however you save 35m.