Dumb question about paying investment fees

[rfisher]

I expect that the answer is that it depends.

The question is - is it better financially to pay investment fees for ISAs / GIAs from cash deposited for that purpose and not invested, or by selling down from the ISA / GIA invested funds?

Showing your workings with numbers would be interesting

[Jon39]

Quite easy to find capped ISA fees, at just £3.50 monthly.

With such a miniscule amount, in relation to what the total ISA value might be, I don't think the method of payment would make any significant difference at all.

Selling down should not be necessary, because surely there would be a steady inward flow of dividends.