Current prices are all over.
CMP versions run from $750 and up--but, those are gone over gunsmithed-good examples.
Gunshow beaters (in Texas) start in about $1300-1500--and none of those come with ME or TE gauging, all sorts of importer marks and stocks finished in used motor oil. Armslist examples seem to hover in about two grand. GB examples are all over the place.
As to accessories:
Slings are pretty available in repro; a little steeper in legit wartime examples. The cloth sling is around $40; a legit per '42 leather sling is going to be $80-90. GI cleaning kits are about $25, the multi-tools are stuck about $30-35.
Bayonets are a mixed bag. M-1905 16" with scabbards are going for $250-350; M-1 !0" with scabbards are $150-200; the M-5 bayonet that uses a stud into the gas tube plug are $125-175.
The WWII issue cloth muzzle covers are about $10 (and really ought to be $5--they are everywhere). You can get a set of nylon muzzle & rear sight covers for about $20 (and your safe will thank you).
The en bloc clips are still plentiful. Anyone charging you $1 each is ripping you off. But, the days of 20 for $1 are a bit past (but, there are bulk lots available, if you are willing to look, but you're buying 250 or 500 at a time).
The carry/drop bags are still out there, but the legit military ones are in bad shape as they were never meant to last 75 years. The PRC knock-offs might as well be lined with sandpaper, for the materials used.
You can find unopened boxes of M@ ammo, but they are very dear (and open boxes are a bit like shooting dice with Bad Leroy Brown). But, there are a couple of ammo manufacturers who are making specific-to-Garand ammo that will not require and adjusting gas plug (but, the adjusting gas plug is a simple add, and a great boon to shooters).