You are right you need to be doing 1,000's to really see the saving. 30 years ago you could save a fortune now the saving is not so great, if a few of you club together and buy and load in bulk then you will save money. Given a good loading machine and having everything to hand a couple of you can load a 1,000 or more in an evening.
Where good savings can be made is on the larger gauges and ofcourse the "obsolete" size cartridges. I save £'s on the eight's but they are all loaded by hand and take much longer.