This is one of the best discussions (informative and civil) that we’ve had on EFI yet! I agree with Daytona Turbo and MoparRich completely, higher-hp engines make a TBI setup less attractive. I don’t have any radical or 400+hp engines so the benefit of sequential tuning isn’t foremost in my mind.

I’ve scored 3 different 454 TBIs for around $75 each (the earlier ones with the 90lb@13psi injectors) and there is a guy on ebay that will bore them and put thinner blades in for about $175 shipped. One just has to be patient and bid on a lot of them to get a cheap one. Having a smallblock TBI for parts (dirt cheap) sometimes allows you to score a bare 454 casting cheap, too.

There are a few places that sell stiffer regulator springs and/or adjustable regulators so the fuel pressure can be turned up to 30+ PSI easily (which is the pressure the later-model 454s ran at). With a little ingenuity the regulator can be made adjustable at home for free.
90lbs (@ factory 13psi) = ~ 300hp, >>106lbs @ 18 psi (~360hp), >> 125lbs @ 25 psi (~425hp)

Yes, TBI cost goes up with hp level , but if you want port injection you either need a modified intake ($300 to ???), fuel rails ($75-100), a regulator ($100+), and injectors ($100-400 depending on size) plus you still need a throttle body for the air (all the 4V styles are $300+, and an elbow and single-bore TB is not much cheaper). At least if you run an RB there are 2 off-the-shelf intakes available (the Eddy Victor and the Eddy ProFlow XT) but those are $300 and $450 each. And if you’re a stock-head B-engine stroker guy, nobody is making a port manifold for that one.

And one thing we haven’t mentioned yet – if you want to hide EFI for a near-stock engine appearance TBI is the only way!

Anyway, I’m gonna start TBI and go from there because it’s simplest (thus far I’m all research, theory and fabrication, but millions of TBI cars prove it does work). I will eventually go to port as experimentation time permits. Hopefully I’ll have some results to report next spring!