The Alpine crowd don't mind spending serious money. They are just after the internals as you can just slide the gears onto a different pinion shaft. I have also seen them splice different pinions onto the shafts (!). As to price, I couldn't say. If you can find a rusty hulk with an owner who doesn't know what they have, you could get it for a song. Otherwise, 1K to 2K euros? A Lotus 365 sold in France this year for 1650 euros. A Lotus 365 in the US went almost instantly last year when it was listed at $900US.
The Lotus 365 gives nice even steps in the first four gears, then a large jump to 5th. First is a bit low (3.6) though not as bad as with a later 395/NG3 (3.9 and 4.1). An early 395 gives a better first gear (3.4) and close steps between the first three. Bit of a jump to 4th and then a very small step to fifth (0.91). You can, however, easily fit the 0.86 fifth from the later 395. This gives a nice set of ratios albeit with a bit of a gap between 3rd and 4th. The R17 365 has the same 3.4 first as the 395 and a 0.93 fifth with all the gears nicely spaced. Of course, the 0.93 fifth will be a screamer on the road, fine for the track though. Some people have managed to fit the 0.86 5th from a later 395 to a 365 but it is not a bolt-in job.
Bored? Lonely? A kind previous lister made up an Excel spreadsheet with all/most of the various Renault boxes listed. You can also vary wheel sizes. It gives you a speed in gear chart in 500 rpm steps between 2K to 7K. Ping me at j b c o l l i e r AT s h a w DOT c a and I'll send you a copy.