The problem with varying tech levels on worlds is a relic of the random UWP generation system - just like a lot of nonsensical things in Traveller. There's been a lot of discussion how you just wouldn't find some TL7 world right next door to a TL12 world when they're both members of the Imperium, the TL7 world doesn't appear to be poor in some way, nor is the TL7 world interdicted or an autarky (it's particularly ridiculous if the TL7 world is industrial).
I have a (not necessarily canon) view of Tech Level in Traveller that readers of this board might find handy:
Tech Level is extremely biased by what kind of goods the world can offer a Free Trader who visits the world to fill his or her holds to go off to the next world and the likely markets for goods he or she has in his hold already. Likewise, there is less emphasis on what is actually in use on the world by its natives. This neatly explains why much of human history simply lumped into TLs 0-4, despite all the great strides made in those TLs, the goods produced by those TLs will only be of interest as curios and therefore not much interest to merchants for hauling.
Similarly, I'd say that on any world that does not have some sort of ban interstellar trade, you're going to see much higher TLs in use on the world. The closer the TLs to Imperial Standard (TL12), the more higher tech you'll see; a world with TL4 simply doesn't generate the wealth to trade to purchase off-world goods; they're likely to get their foreign exchange by trading resources. Resources are typically controlled by a few landowning elite (even in a "democracy") and the wealth will naturally flow into their coffers. As they'll sending that wealth off-world to get more high tech goods, they won't be investing it in their homeworld; there'll be an epic wealth gap as a result and only the super-wealthy will have (lots of) off-world goods. Even in the case of a world of freeman farmers at TL3 or something, their crop yields are so low they'll take forever to accumulate tradeable wealth, so the number of high-tech goods in use on the world will be limited (of course, some visionary and charismatic person might organize said farmers into a cooperative and increase yields through the use of technology but the cases of those where that one person doesn't end up being a land baron I think will be rare).
As TLs rise, they will have more things to trade and wealth tends to (slowly) be spread out more on the world as enterprises not directly tied to resource exploitation become more significant. The accumulation of wealth (wealth recognized by interstellar traders) will allow more off-world goods to be afforded. By TL7 or so, many things on the world might be TL12 - hospitals might be equipped all with TL12 medical gear, personal communication might be all TL12, and so on. However, the world's own native industries could still only produce export goods up to TL7. Still, the world might be pretty wealthy if they have some hybrid of TL12 and TL7 machinery and devote much of their world to Agriculture and there's some industrial world nearby that needs foodstuffs.
PsiTraveller said:
Anyone have rules or experience with players wanting to leverage higher tech capabilities on a lower tech world? There is a lot of profit to be made bringing in the TL 8 widgets to a TL 7 world, let alone the TL 12 gear.
There's a proviso I'd put in as an old Traveller player: Don't let your players make a killing importing high-tech goods to a low-tech world. I know this sounds like Opportunity (tm), but this is the Traveller universe. There's hundreds of thousands or millions of other free traders in the Imperium who are lean and hungry (and possibly desperate) pouring over maps of the Imperium looking for opportunity just like the players. If the players can think of it, so
have at least a hundred people who are in a position to do something about it. There may be opportunity there, but it's likely that others are already there doing the same thing; if it hasn't worked so far, there's a reason for it. If it does work, others are doing it and have established markets. Players could find a niche though.