MyISAM around 5x slower than InnoDB
1) InnoDB will go faster with indexes, too.

2) InnoDB with appropriate indexing is the best solution.

3) MyISAM has been slower than InnoDB for most workloads for well over a decade. There are fundamental difference in how memory and caching work between the two.

In this case InnoDB was picking the first row by primary key. Since InnoDB tables are clustered by primary key, this was very fast, and PK was likely already in memory from when you created the table.

Create an index in BidHigh and it'll go even faster.

Unless you have an overwhelmingly good reason to use MyISAM - you shouldn't. And if you think you have an overwhelmingly good reason, you should re-scrutinize it because they are vanishingly few in 2020.