I'm in process of switching to IB, so I'm trying to understand a few things. On the fixed pricing, I see that the minimum per-order is $1 (so a buy/sell is $2). On the tiered structure though, there isn't a specified minimum spelled out too clearly, it's tucked as a footnote (#3): So is it really a $0.35 per-order (one way, $0.70 round trip) fee on the tiered side? That seems kind of contradictory, since I've seen people say that the fixed pricing is best for lower volume trading and you really shouldn't go into the tiered until you're doing higher volume. It's a silly example, but if you're trading 10 stocks a month, that's $3.50 on the tiered vs $10 on the fixed.
Generally it goes as follows: if you do mainly LMT orders then tiered is best, if you do over 500k shares per month then tiered pays off (easily accumulated when trading sub $5 shares). The pricing is very balanced at the moment, there isn't a CLEAR benefit to either if you do MKT/LMT somewhat equally. As you already found out, the minimum is $0.35 but you need to add all the various fees to get a realistic number.