I know,
@Caveeagle. I was trying to describe the more general situation and not take into account ways to minimize cost. For those of us in the US who don't live in FL, CA, etc., a trip to the Pacific to dive a reef can be expensive, too. I was just pointing out that, absent cost-saving measures or circumstances, cave and wreck are generally expensive endeavors compared with reef diving. To make a generalization about relative "bang for the buck," I am assuming one doesn't live near caves, wrecks, or reefs, and needs to start from scratch with training and gear. That's the general case, and apparently not the OP's case.
my basic technical rig vs. my basic recreational rig
I have 2 tanks for both, recreational they can be split, technical they are either banded together or on my sides. Either way you have 2 tanks, 2 valves. Used doubles are not really any more expensive than buying tanks as singles, so wash on tanks. Roughly $500 on the high end for a good set of doubles on the used market.
I use a bp/w for both, or a sidemount rig for both, but either way it is the same plate/harness for both. My sidemount rig is the same for al80's up to LP121's, thanks Hollis Katana, and I have a doubles wing for doubles and a singles wing for singles. Wash on the buoyancy compensation department. Roughly $500 here.
I have one extra first stage for double tank vs. single tank, but many seem to be diving pony bottles, and if you shop around you can buy a doubles or sidemount reg package for not much more than a singles reg package, so call it $150-$200 more for the regulators. I advocate purchasing doubles/sidemount reg sets for recreational divers anyway because the extra first stage can save them an emergency repair bill if they have a failure which can cost them at least one dive if not more if the boat doesn't have a spare for them to borrow until they can get it fixed. $600 for singles, $750 for doubles, $800 for sidemount *prices based on Dive Rite XT sets from DGX*
Fins, mask, computer, exposure protection, all the same. So for an extra $200 in gear I have a setup that I can do some pretty legit cave diving with, and an extra $600 or so if you put an O2 deco bottle in there to open up the diving that much more *$550 for the Dive Rite XT reg and tank/rigging setup from Cave Adventurers*. That is hardly a significant extra expense in the grand scheme of things. Grand total is $1900, plus fins/mask/computer/exposure protection, ~$3k total in gear to dive some incredible environments with top of the line gear, and everything except the tanks is brand new. Not that much more than what most recreational divers shell out for "basic" equipment.
The problem is most people don't buy gear with the end in mind and up having to replace a bunch of stuff because an idiotic/ignorant and/or greedy dive shop owner/instructor convinced them that a plate was "technical" gear and was beyond them, and sold them a bunch of stuff they don't actually need. Not the persons fault necessarily because the industry is what made them like that, but it is what it is. Point stands, that for a negligible difference in gear costs you can get setup for doubles/sidemount, or single tank. Nothing wrong with single tank, I have it for a reason, but I also don't dive it hardly ever for a reason. I will always *unless expressly forbidden for some reason* take a pair of light/small doubles out before I take a big single tank *double 72's vs a 130*, and I will take a big set of doubles out before I take out a pair of big singles. If renting tanks, I will take my independent doubles bands and throw a pair of something in there if I want to dive backmount, or dive sidemount.
But cave diving isn't for everyone.
