>what are the transaction costs like for buying and selling physical gold/silver?

This depends on soooo many factors (mainly: mint, store, and your relationship(s) within). I buy and sell both stocks and bullion on long-term (years), and am typically only selling when I get over-extended on a project (construction renovations) and absolutely need liquidity [e.g: today's visit]. Young-forty-something.

But today at my US coin store (in a no-tax state), you could buy/sell a Canadian Mapleleaf (an ounce of 99.99% gold in easily-recognizable coin format) for 2.5% spot. For real physical gold that you can hold & hear (isn't fake/heavily-leveraged "paper gold").

I never recommend anybody transacts less than an ounce because the fees rapidly increase on smaller denominations (e.g. tenths are fee-prohibitive, other than as less-expensive gifts for recent graduates). Buy ounce coins, long-term, at regular intervals (no timing the market, only time IN the market!).

Silver is a wildcard, at least at my local shops. Today it cost me 6.5% to unload a few hundred ounces — which sucks, but shops are buying lots of silver right now given its recent increases; this increases their risk (should the market correct, which it probably will around $100 IMHO). Typically this would have been about 4.5% — still, I more than quadrupled my original investment (from just a few years ago).

So definitely you shouldn't be buying/selling bullion short term (fees will eat you alive!) — but it is always nice to have an emergency fund that isn't fiat (i.e. losing value guaranteed) but is also immediately convertible back into currency (no mail / ACH / bank delays).

I have about a year of my normal income in physical bullion. Most I've been holding on to for years — which is how you should transact physical metals. Timing any market is impossible... it doesn't always even rhyme.

[•] https://en.wikipedia.org/wiki/Dollar_cost_averaging

Disclaimer: I am a forty-something electrician — not your financial advisor — and am the type of risk-taker that has "stupidly" taken 10% of his paycheck in bitcoin/bullion, since 2013.